Excel interpolate from table. Interpolation is the process of estimating an unknown value of a function between two known values. Excel interpolate from table

 
 Interpolation is the process of estimating an unknown value of a function between two known valuesExcel interpolate from table 96 and speed 1100 result 56

It seems that the best match is the quadratic that goes through 0, i. 2: subtract the smaller value from your input value , subtract the smaller value from the larger value , divide the former by the latter. 26 2M 0. Interpolation. Method 4: Using FORECAST Function. Since the surrounding cells of the missing value are D2 and D4, we will select the range D2:D4. Enter the data. Messages. interpolate ( axis =0, method ='linear', inplace =False, limit =None, limit_area =None, limit_direction ='forward', downcast =None, ** kwargs) Axis represents the rows and columns; if it is 0, then it is for columns, and if it is assigned to 1, it represents rows. Messages. Step 3: Prepare Dataset According to X and Y value. When using Excel, there are two main ways to use linear interpolation. To start, place at least two columns of data in an empty Excel worksheet. Use of Linear Trend Method. Linear interpolation is the process of estimating an unknown value of a function between two known values. This table will be used as the lookup table to perform the interpolations. The function Table. Using the Equation of the Linear Interpolation. Step 4: Determine Interpolate Y Value Using User-Defined Function in Excel. If we consider two columns of data, for example: A B 100 97 110 120 135 135 157 166 What function or nested functions will return an "A" value if I input a "B" value of 147 ? Learn how to interpolate and extrapolate in Excel. But some columns of my table has NaN values and the. These are stored in dat files in a format of: So I have one long file of over 4 million rows for each year. xla, delete it, save the new file and seek. 5). A (x 1 ,y 1) and C (x 2 ,y 2) are the two points around B. richthorpe, this post is unlikely to be very useful for your purposes, but you may get some interest from it. 4. which would have target achievement values from 101% to X%, and corresponding bonus award amounts ending at 100% - and then vlookup will be made in that table). I don't want to restrict myself to the two blank sequences in the test data by manually doing it each for each sequence. We can use INDEX and MATCH to pull the values from the spreadsheet into the linear interpolation VBA function, but there’s a catch. By using the above data, let us create a interpolate function and draw a new interpolated graph. Surprisingly, linear interpolation is quite hard to do in Excel. I created a steam table calculator which makes it easy to calculate the thermodynamic properties of water in the subcooled, saturated, and superheated region. If I assume that it must be done in Excel. linear(a2,c2:d2,e2:f2),na()) When I try to move the table and the interpolation cells, the results can change or be lost. 3. I have also tried interp1 function to interpolate. We can mea-sure the length of the intervals a and b (simply by using a ruler). Ideally, you'd create two columns for the x values and y values. You can (Copy the data range and) convert horizontal data to vertically excel in 3 ways. 1<= Y <=0. In that case save the startRate and the changeRate for interpolation. Type the function related to the interpolation that you wish to solve. How to Multiply Column by a Constant in Excel. You can linearly. With Excel it’s a little more complicated; you can use the FORECAST. Also, it calculates (or approximates) the. In between each column after the first one, I would like to add one which contains the month preceding it, and the interpolated value based on the preceding and next column. 4) Solve y=mx+b to interpolate. Step 2: Next, gather as many as possible historical and current data points in order to build a function. scipy. Map a set of scattered (x,y) data points onto a uniform grid for curve plotting. 65, the probability is 0. As the highest number in this table is 32, I need to generate a column with 32 cells, B1:B32. The function below will interpolate or extrapolate any table. In this article, we will learn how to add a trendline to our charts. 2 0. . Given an X vector, this function interpolates a vector Y based on the input curve (XY Range). 5 in this case. Click the Table > Design > Table Name >. Example: Linear Interpolation. Double Interpolation is very familiar to Engineers who are using it for every Design ProblemsThose who want to do Double Interpolate in excel this Video will. Then, we will head to the Home tab and select Fill in the Editing group. Using the Trendline, Excel can fit. interpolate with. 4 -0. Ive been reading about interpolation and bilinear interpolation at the forums and it seems like you need to have "linear" non-scattered dataset. This is a simple double interpolationThe reference table used in the video is Table 19-from IS456:2000. Then you can use this actual equation to interpolate the value. As an example, if you want to find the saturated pressure of water at a temperature of 40 C you can look in Table B. 4 MPa and T = 72 P oC, the enthalpy can be estimated by interpolation using the rows from Table A. Now we can find the missing rows, and the real rows on either side (for interpolation): DECLARE @Missing table ( x integer NOT NULL PRIMARY KEY, prev_row integer NULL, next_row integer NULL ); -- Find missing rows INSERT @Missing (x, prev_row, next_row) SELECT Missing. Shows how to set up a cell to automatically do linear interpolation in Microsoft Excel. In this case, the values in cells D3 and D6 are missing. Remember that likely none of us on this side of the internet has done this sort of calculation. ‘Table – The range of values with at least YCol columns ‘YCol – the column of Table used for the Y-side of the interpolation ‘Dim TableRow As Integer, Temp As Variant Dim TableRow As Long, Temp As Variant ‘see below Dim x0 As Double, x1 As Double, y0 As Double, y1 As Double Dim d As Double ‘TableRow – the row of Table that is. For example, you select “Canada” and “VAT”, you want to get 5% in return. With optional arguments, you can control the interpolating spline properties. Is there any way to interpolate on a range within a Calculated Field? (Or any other good way to accieve this). =Interpolate($A$1:$A$3,$B$1:$B$3,D1,FALSE,FALSE). This is a video that will show you how you can solve problems related to Thermodynamics using Steam Tables and by applying the concepts of Linear Interpolati. Implementing Interpolation with Microsoft Excel. (a) The program must be able to handle any of the fluids from the given Excel spreadsheet (Air, CH4, Bi, etc. Interpolation. First, we’ll fill all the rows in the column labeled “As/Ac. I would want the code to interpolate between the values and split out the interpolated power value for each WS in the "WS" pandas table. x FROM ( -- All. 4 0. The following step-by-step example shows how to use the TREND function to extrapolate data in practice in Excel. So what i want to archieve is something that check if a number is in the table and if its not it needs to interpolate. Interpolation is a method of estimating and constructing new data points from a discrete set of known data points. 674), for 40 C in the first column. . Open the "Data" tab and click "Forecast Sheet" in the "Forecast" group. 4); three times each to determine the points p1 and p0 as illustrated in the 2D bilinear interpolation, then one more time to compute the point p. To extrapolate data by formula, we need to use two points of the linear chart that we plotted before. ‘Table – The range of values with at least YCol columns ‘YCol – the column of Table used for the Y-side of the interpolation ‘Dim TableRow As Integer, Temp As Variant Dim TableRow As Long, Temp As Variant ‘see below Dim x0 As Double, x1 As Double, y0 As Double, y1 As Double Dim d As Double ‘TableRow – the row of Table that. My final data sets will consist of a couple hundred sets of data with each set containing 35-55 data points needing to be normalized to. 1. I needed to do a bilinear interpolation of Thermal Conductivity from a 2D table of temperatures (columns) and pressures (lines) -> k (P,T). Applying the FORECAST Function to Do Linear Interpolation. I will use your fantastic Search&Interpolate method to calculate across a table that is composed by X1 Y1 , X2 Y2 , X3 Y3 ,. You can monitor the calculated values in the Visual Basic Immediate window. Identify your data. linear interpolation, log interpolation and harmonic interpolation, especially for statistics tables. use this with index and index +1 to find to two values around your input. Step 1: Firstly, identify the independent and dependent variables for the function. The code to interpolate is basically a one-liner, from scipy. Here, we have a dataset containing the values of X and Y, where Y=F(X). The values along the top (5,10,15,20) are relating to values of dx. In this method, we will use a VBA code for searching a value in a range, and then, get the desired result with the help of the interpolation. Hi! I am trying to compute the design moments that a slab should carry using ACI Coefficient method. Firstly, we will use the known and surrounding values to find the missing values. Time series B has more data points, at irregular intervals, over a shorter time span. Select the range of 12 data points for the X Function Argument field. 2. First, you need the data graph so Excel can fit a line to the data and g. Setting upper and lower limit for an Excel histogram. For instance if I look up 130, and my table has values in column 1 of 100 and 200 (in the first and second rows). . I was able to piece one together. Hi, I have a table of x and y values and I wish to be able to look up an x value and get the corresponding y value. The calculation step goes fine, but the file size at one point topped 160 mb. Click the insert function button (fx) under the formula toolbar; the dialog box will appear, type the keyword “PERCENTILE” in the search for a function box, and the PERCENTILE function will appear in the Select a function box. In mathematics, linear interpolation is a method of curve fitting using linear polynomials to construct new data points within the range of a discrete set of known data points. GRIDXYZ is a powerful 3D data gridding function based on natural neighbor interpolation algorithm. For the sake of overview, we put this into a table: x x 0 x 1::: x m y y 0 y 1::: y m For. . Using the Trendline, Excel can fit exponential, logarithmi. Cubic Spline Method: This method fits a distinct cubic. 2 0 0. Locate where 12 bar a (A) would be. Jerry. Every time you change one of the referenced values the calculation will be run again. columns) # for i in range (0,N): # df. Step 2: Input Required Data into Cubic Spline Model. LINEAR Function. do a linear interpolation. I've been trying to work on a workbook function that will see the number that I'm looking at, find that number between two others, and then report back to me the vlookup value associated with that interpolation. Range ("g3"). The equation y = y1 (x – x1) (y2 – y1) / (x2 – x1) All of the values used in this formula—x1, x2, y1 and y2—are known. data points exactly by simply using linear interpolation between the known values. 226, which multiplied by 950,000 is 1,164,960. To do the interpolation for input values that lie between the index values in the table, the following are needed: The row number of the smallest vertical index value that is greater than (or equal to) the vertical input value vnum. What I would like to do is interpolate {log(x. To interpolate this value, use the following simple formula: (x – x1) * y= y1 + (x – x1) x=22. Once the index number is returned, you can use. tutorial for linear interpolation in Microsoft excelexcel formula: =FORECAST(B17,OFFSET(KnownY,MATCH(B17,KnownX,1)-1,0,2),OFFSET(KnownX,MATCH(B17,KnownX,1)-. Right click on your chart > Add trendline > Under Trendline options, select one by one and see which is the best fit > Go down and check Display Equation on Chart. 3. Qb/Qc. The user should enter the the temperature and the code returns the corresponding viscosity. Calculate the intercept c for the given row values. Time Series in Excel 2003. 2 AOA, I want to find out the corresponding Cl & Cd. Dec 15, 2011 #1 Hello - I have a family. MATLAB Data Interpolation - Basics. Linear Method: This method calculates the data by applying an exclusive linear polynomial between every pair of data points for each curve or for a set of three curves for surfaces. Thread starter Pigankle; Start date Dec 15, 2011; Tags interpolation lookup P. One of the basic approaches of data. There are 7 tables with different values of B parameter (-0. If we consider two columns of data, for example: A B 100 97 110 120 135 135 157 166. If I calculate it with the data you have given: Temperature 29. c. In MATLAB, you should use the function interp1. xlsx. A simpler option is to choose a nearby but conservative option (one that results in a slightly higher p-value), or you could just use the closest table entry. Step 2: Add the TREND formula as shows in image 2. 1. If the r0 value falls between two values a function needs to interpolate and get the value for that specific r0 value. Converting Data to a Table. The values along the side (180,185,190,195,200,210,220) are LE values. g. Method 4: Using FORECAST Function. Table of Contents hide. Linear interpolation, also called simply interpolation or “lerping,” is the ability to deduce a value between two values explicitly stated in a table or on a line graph. Not sure if even XonGrid is really kept up. This is the only method supported on MultiIndexes. 3) Linear interpolation (I sometimes use the TREND () function) to return the correct y value for the new x value. Brian's approach will interpolate any function that has function values for integer arguments. The general expression for the trilinear interpolation is given in Eq. Performing linear interpolation in Excel is quick and straightforward. Method 2: Interpolate in Excel Graph Using Trendline. It calculates the dependent variable (Y) for a given independent variable (X) by fitting a straight line to the available data. forcast wants a range or an array and not numbers which is what you are passing with indexys:indexys1 You are passing the values of the index, so it would return something like 104:34 and not a range or an array. if the value to look up is in A1, the range of data a2:A10 and the data sorted ascending. I expect that a simple linear interpolation would suffice for this project. I have a specific point of temperature and pressure and need the thermal conductivity interpolated from them. We can use the following basic syntax to perform linear interpolation. the excel file make a first linear interpolation on pressure and a second linear interpolation on temperature. These values need to be in increasing order. The basic idea then follows these steps: Find the indices of the values in x_values which define an interval containing x. . xll and for the 64 bits version of Excel select XonGrid-w64. then have MATLAB take the average of the temperatures and use it to search through the Excel tables to find the values of viscosity, conductivity, etc. Call the value that comes before B1. The corresponding desired pressure is then in the next column; in this case, 7. 1. INTERPXY is a versatile 2D interpolation function based on splines. Select a cell. This is the easiest way to interpolation by set up formula only 1 time and we can use this forever. 2239x2 – . Method to calculate interpolation step value in Excel - Microsoft 365 Apps | Microsoft Learn ข้ามไปยังเนื้อหาหลักYou could then save these values in your table (only copy them as values). Use INTERPXYZ to interpolate a set of scattered (x,y,z) data points at arbitrary (xq,yq) points. Examples. See an example of linear interpolation with a table of data and a formula. Thanks in advance for your valuable suggestions. How to use: Insert the code in a module in the spreadsheet where the function is needed. I have the question if this could be extended to interpolate linearly over 3-D function F(A,B,C). Method 1: Mathematical Equation for Linear Interpolation. Performing Interpolation to know the temperature of weather during different time zones. For x1 and y1, use the input and output from the lower value, and for x2 and y2, use the input and output from the higher value. 2. . It can be used to probe the value of a surface passing through a set of scattred data points at arbitrary points. The worksheet is set up to interpolate a data set of up to fifty points to a new data set of up to fifty points. Description. 4 0. I would like to write an Excel function that linearly interpolates between data points. Select your data > Data > Insert > Table (Click the checkbox the My Table has headers. Messages. The Analytic, Interpolation, and Piecewise functions can also be added to Materials. You can then transform it back to linear scale. , I have a table with different cases from A3 to S3 and an m value ranging from 0. Interpolation technique to use. This uses Excel Forecast function =FORECAST (x,known_y's,known_x's). Hello all, I just wanted to stop by and share my work. tutorial for linear interpolation in Microsoft excelexcel formula: =FORECAST(B17,OFFSET(KnownY,MATCH(B17,KnownX,1)-1,0,2),OFFSET(KnownX,MATCH(B17,KnownX,1)-. Select your data > Data > Insert > Table (Click the checkbox the My Table has headers. You can use them to perform simple table lookup, as well as, interpolation and extrapolation from tables with one, two or three independent variables. Instead you should 'add trendline' choose the type of relationship the x and y data share (or you believe works best) and click 'Display Equation on chart'. Using the Trendline, Excel can fit exponential, logarithmi. 2) Calculate slope and intercept for each pair of points (for each firm) as part of the lookup table. This template allows you to quickly perform a linear interpolation (and extrapolation) between a flexible data set, up to a maximum of 50 sample data points (rows). A short introduction to using linear interpolation to find intermediate values (i. First, organize your data into two columns with known values. You can easily use the MATCH function to return the location of your unkown value. Scipy provides a lot of useful functions which allows for mathematical processing and optimization of the data analysis. With XLOOKUP, you can look in one column for a search term and return a result from the same row in another column, regardless of which side the return. As the highest number in this table is 32, I need to generate a column with 32 cells, B1:B32. o In the code window that opens, paste the code below. It allows you to incorporate table-driven modeling directly in your custom block, without the need of. Interpolated ENR table example HP 346B noise. I know how to get value that is in "cell" of that table using. Once we have our data set, we must create a chart based on those values. xls, since then it will not be available to other users of the spreadsheet. The corresponding desired pressure is then in the next column; in this case, 7. 10) interpolate_look_up_linear = value_ser(i) ' if the look_up value is the same as a value in table set to value Exit Function End If If lookup_value < lookup_ser(i + 1) Then ' case where the look up value is. 3 Torque. For a given (PSI, GPM) pair you can find the four neighboring known data points: in the case of (2300, 4. and the plot looks like (Scatter with. What is the best way to interpolate in such a dataset (so I have a value for every day) ?Use the XLOOKUP function to find things in a table or range by row. INC(<column>, <k>) Parameters. 2. Click the Table > Design > Table Name > Enter T_Inputs > Press Enter. ★ Want to automate Excel? Check out our training academy ★ Download the example file★ for a temperature of 29. Then select Analysis: Mathematics: XYZ Trace Interpolation from the Origin menu to bring up the dialog. A (a, b) B (c, d) The linear extrapolation formula is: Y (x)=b+ (x-a)* (d-b)/ (c-a) You can enter the formula according to two points of your data values and extrapolate the target value. One-dimensional interpolation. Excel has the =FORECAST. When installed, TriLookup adds eleven powerful lookup and interpolation worksheet functions to Excel, which offer greatly enhanced functionality compared to Excel's built-in lookup functions. You perform two independent linear interpolations on PSI, and then a final. 4 -0. 1, (p. 24 1M 0. 1. (Linterp is developed to do the same thing as the Mathcad "premium feature" linterp. I selected my chart and chose 'Select Data' to bring up the Select Data Source dialog box. In this example, we want to find out the missing data. I have made an example. I would like to be able to input into three different cells: Weight, Temperature, Altitude, and for the formula to then look up the weight, then the temperature and then the altitude. Step 1: Create the Dataset. However, you may use similar techniques in other place. Using the TREND Function. More precisely, I would like the macro to account for X values <0 or >0. Linear Interpolation. See examples, formulas, and tips for accuracy and error prevention. Unable to download your file. Re: interpolation in an array. for univariate polynomial interpolation can be recovered from the LU factorization of a Vandermonde matrix. Linear extrapolation is the same as linear. If you think the result should be 157: The table would need to be sorted in. For example, look up the price of an automotive part by the part number, or find an employee name based on their employee ID. You can input a few. For detailed instructions on how to do nonlinear interpolation within an Excel. As an example, if you want to find the saturated pressure of water at a temperature of 40 C you can look in Table B. Excel Questions . Linear interpolation. Does anyone have experience in ways to streamline the interpolation process? I need to interpolate ~8 values from ~15 tables, over 12,000 times each. but look at index and match functions. Hot Network QuestionsIf you must stick with tables, my preference is to keep track of probabilities on either side of the true answer. Include your Excel version and all other relevant information. Inserting INDEX- MATCH with FORECAST Function to Interpolate Between two Values. has the formula as shown below. Public Function InvBilinearInterpolation (xRange As Range, yrange As Range, zRange As Range, xyCoord As Double, xyPick As String, zCoord As Double) As Double ' This is a reverse bilinear interpolation. Aug 19, 2016. การ Estimation กับ Interpolation ต่างกันยังไงครับ . suppose dates are in column A with values in column B, and that B2 is to. fwk Table_Interpolation. One of: ‘linear’: Ignore the index and treat the values as equally spaced. Now, we will show you how you can interpolate polynomially the value of Y from the given value of X by drawing a scatter chart in Excel. Time series A has weekly data, but with two values omitted. It allows you to do linear or spline interpolation for a general curve in n-dimensions. 1) Select an empty cell for the output. and A2 has the value 2, B1 has the value 5 etc. Rows. Method-1: Using the IFERROR, VLOOKUP, and AVERAGE Functions to Do VLOOKUP and Interpolate Method-2: Combination of IF, ISNA, VLOOKUP, AVERAGE,. Step 3: Prepare Dataset According to X and Y value. Vector x contains the sample points, and v contains the corresponding values, v ( x ). If you're stuck working in Excel. Answer to Below is a portion of a steam table used in. That. A simple solution will be the so-called bilinear interpolation. You could change the Forcast line to: Sheets (1). I mean It might be 3 tables with B equal to: -1 0 1. In the spreadsheet, insert the formula: =interpolate (X, [XRangeReference], [YRangeReference],<param>), where X is the value you wish to. , time) and another for the dependent variable (e. Step 2: Creating UDF with VBA. The first step to performing linear interpolation with this method is to create a chart with all of your data to optimize your organization and ensure accuracy in your calculation. Choose the Scatter chart type and select the scatterplot. Select or type the argument as requested by the function [Example: F6,C5:C11, etc. The question is, both Trend method and Vlookup method are not working for me. Cubic Spline Interpolation in Excel: Step-by-Step Procedure. Copy and paste the following VBA code to the new module that has been created. Joined Apr 18, 2011 Messages 32. Interpolation (scipy. 4 is: =FORECAST(F2,C3:C4,B3:B4) This simple method works when there are only two pairs. Transcribed image text: Below is a portion of a steam table used in thermodynamics. be interpolated for A2 from A1:B1 and A3:B3. I have found fomrulas for vlookup and xlookup but not for hlookup. Interpolate input data to determine the value of yi at the points xi. 4 you should just be able to use lookup to get the values for 219 and 220 (I'll call them 3 and 4 for example) and then take a weighted average: 3 + (4-3)* ( (219. If y is a matrix or an N-dimensional array, the interpolation is performed on each column of y . For example, look up the price of an automotive part by the part number, or find an employee name based on their employee ID. You just need to insert the formula. Simple Mathematic formula Linear interpolation is the process of estimating a new value by drawing a straight line between two nearby known values. 1. 5 (in addition to 0. Next I clicked the 'Hidden and Empty Cells. Let’s try to break the above formula and understand the formula in detail. Linear Interpolation can even predict values for rainfall, geographical data points, etc. For instance, for x=3 with your example lists, the containing interval would be [x1,x2]= [2. . Put the values of the data into the linear interpolation formula. So here's the deal, I work for a company that does "floor lifting". There's not really that much data I'm dealing with and I've avoided known memory hogs like vlookup, etc. 2) The INDEX () function to return the four values (2 x values and 2 y values) that bracket new x. g. A common application of 2D tables is ' to interpolate a z value in the body of the table from x and y values in the ' table headers. =B1+ (A2-A1)* (B3-B1)/ (A3-A1) in B2. How to Check if Number is an Integer in Excel. Its general formula is. 1. Clear searchBasically, the Excel formula is simple: =_X1+ (_X2 – _X1)* (Y – _Y1)/ (_Y2 – _Y1) Linear Interpolation [/captionThis formula can be written in a more familiar style, the relationship between the known. Based on audio signal frame power (in dB), I could search for appropriate gain from the table. Use of Linear Trend Method. 0. Lagrange Interpolation Example Suppose we have got points x 0;x 1;:::;x m and values y 0 = f(x 0); y 1 = f(x 1); ::: y m = f(x m) of some function f that is otherwise unknown. Use the tablelookup function in the equations section to compute an output value by interpolating the query input value against a set of data points. Follow these steps: Start with the worksheet shown in Figure 63. WorksheetFunction. I cannot use xlookup becaus eogf the. T 259. Fortunately, it’s easy to do that in just three simple steps. 3) A lookup function (usually using approximate match option) to return slope and intercept at the specified date from the monthly table. There are other Excel tools that we can use to project/interpolate values, such as Analysis ToolPak or Microsoft Solver Foundation. 96 and speed 800 result in 48. Step 3Vq = interp3(X,Y,Z,V,Xq,Yq,Zq) returns interpolated values of a function of three variables at specific query points using linear interpolation. . What I need is a complete set of {date, value} pairs where for each date withing the range a value is known (either measured or calculated). Description. Syntax and Parameters: Pandas. X, Y, and Z contain the coordinates of the sample points. 1, (p. For superheated refrigerant at 1. An Interpolation function () is defined by a table or file containing the values of the function in discrete points. You can determine the other coordinate for a new value for y or x by inputting that value. Hi, I am writing a code that is supposed to read values from excel table, the table consists of 2 columns temperature and viscosity. 8), but this number is not fixed. LINEAR must be changed to =FORECAST (depreciated soon). Do Interpolation of Non-Linear 2D Data in Excel. Option Explicit Function Linterp2 (rX As Range, rY As Range, x As Double) As Double ' linear interpolator / extrapolator ' R is a two-column range containing known x, known y Dim lR As Long, l1 As Long, l2 As Long Dim nR As Long 'If x = 1. (First page may look like the image below) 3. But, since either inter-polation process just involves two data points, it will likely miss the general overall shape of the curve that the fitted curve. When the lookup is intermediate of two values in the lookup column, it returns the lesser value from the second column. excel & macro excel & vba interpolation table work Replies: 3; Forum: Excel Questions; V. 0 Kudos. Linear Interpolation in Excel: 7 Methods. , time) and another for the dependent variable (e. For the "Value III" I know the math formula when you interpolate r numbers between two numbers a and b then the distance d between interpolated numbers is: d = (b-a)/ (r+1) And the values of those interpolated numbers are: r1 = a + d r2 = r1 + d or r2 = a + 2*d r3 = r2 + d or r3 = a + 3*d. What I want is to rewrite the linear interpolation function so that it can calculate based off of a small interval.