Discretise into Equal Intervals

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simply90 2014-1-21

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评论： simply90 2014-1-21

I have an array of data, 2 columns and 19 rows of entries, which can be plotted as a loglog curve. However, the x-data I have does not have standard intervals and I need to approximate the curve as a piecewise linear function. Any suggestions as to how to go about this?

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simply90 2014-1-21

Yes. Within x I was considering an interval of 0.07 to fit the data, as it isn't an increasing rate I couldn't make the function interp work as the interval was set, rather than a rate. Thanks so much for your help!

simply90 2014-1-21

It works! Thank you so much Bruno and dpb. I was able to start messing with the interp1 function, I was using the wrong one beforehand with your suggestion dpb, and Bruno your answer clarified it from there.

Thanks for your help!

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采纳的回答

Bruno Pop-Stefanov 2014-1-21

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编辑：Bruno Pop-Stefanov 2014-1-21

在 MATLAB Online 中打开

You can use several methods to interpolate data points from non-uniformly spaced points. There are listed here for one dimension:

1-D Interpolation

Here is an example using interp1:

vq = interp1(c, v, xq)

where x are the (non-uniformly spaced) input points (the first row in your vector) with values v (the second row in your vector), and xq are the query points (your uniformly spaced points). The function returns the interpolated values at xq in the vector vq.

For uniformly-spaced query points, you can use:

x_begin   = x(1,1);   % your 0.005
x_end     = x(end,1); % your 2.13  
numPoints = numel(x(:,1)); % number of points in your original vector; you can change that
xq = linspace(x_begin, x_end, numPoints);

for numPoints linearly spaced between x_begin and x_end. If you prefer to specify the length of each interval instead of the number of points, you could write:

xq = x_begin : int_length : x_end;

with int_length = 0.07.