qinterp1 requires an evenly spaced, monotonically increasing x array. I'm really not even sure what to suspect.Īny help, tips, comments, or criticisms are appreciated. In the limit of large library arrays, qinterp1 has a flat scaling, while interp1 has a linearly increasing scaling (see the image for this file). Or the placement of the interpolation formula. I feel like it has something to do with my notation. The plot for the given data is working fine.
mfile as of right now: function mu_val=linear_interp(T,mu,i) Also include on the plot the results from using a polynomial that goes through all of the data using 1K spacing, and the original data.Īnd this is what I've got down on my. Using this function, create a plot of mu(T) with a spacing of 1K. It is always better to use a built-in tool to solve your problem than to do it yourself, so I might just as well have used interp1 to accomplish this interpolation. Where xval can be a scalar or a vector, and yval has the interpolated values at locations corresponding to xval. Alternatively, you can specify a scalar value, in which case, interp1 returns that value for all points outside the domain of x. Set extrapolation to 'extrap' when you want to use the method algorithm for extrapolation. You can have a look at my answer in this question for an explanation of what interp1 is doing (there is also a graphical explanation in the answer). vq interp1 (x,v,xq,method,extrapolation) specifies a strategy for evaluating points that lie outside the domain of x. The function call should look like yval=linear_interp(x,y,xval) Matlab used to have a clearer documentation for interp1. Write a function in Matlab to perform linear interpolation. Here's the problem as it was given on the assignment: I graphed the given data, that was pretty straightforward, but the interpolation itself is tripping me up. We were provided a table of data for temperatures in K and viscosity of air at those temperatures. Interpolation is the same operation as table lookup. yi interp1(x,y,xi)returns vector yicontaining elements corresponding to the elements of xiand determined by interpolation within vectors xand y. It finds values of a one-dimensional function underlying the data at intermediate points. It also seems that the original MatLab program that I am converting should have used linear interpolation, so the question is probably moot.So I'm working on an assignment that calls for linear interpolation, but we aren't allowed to use the interp1 command. Description interp1interpolates between data points. (2048 data points)Īny thoughts as to how I can get results that are consistent with MatLab?Įdit: I understand that there is some latitude in implementation for cubic interpolation algorithms which probably accounts for the differences I'm seeing. In MatLab the usage is slightly different: yi = interp1(x,Y,xi,'cubic')įor a trivial example the results are the same:
Vq interp2 ( ,method,extrapval) also specifies extrapval, a scalar value that is assigned to all. Vq interp2 ( ,method) specifies an alternative interpolation method: linear, nearest, cubic, makima, or spline. I'm converting a MatLab program to Python, and I'm having problems understanding why 1d is giving different results than MatLab interp1. This results in 2k-1 interpolated points between sample values.
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