Making Different Length Vector Same Length

Question

KH 2019-2-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/446495-making-different-length-vector-same-length

评论： Star Strider 2019-2-22

I have two sets of data, stress and strain. Strain is [9x1] and stress is [12x1]. I need both vectors to be the same length, which would be [12x1]. I have tried using the interp1 function, but in order to use this it seems as though the inputs, which would be stress and strain, have to be the same size already. I am not sure if this is even the right direction. I have provided my raw stress and strain data if someone would like to help or provide any sample code. Thank you in advance!

stress = [1.854621961

397.953227

680.5854525

1319.335498

1569.283812

2489.328323

3585.957167

4591.466307

5916.213652

7592.943924

8625.360283

9808.244251];

strain = [0.001170792

0.005019681

0.010524187

0.017380968

0.026422366

0.034377908

0.04229767

0.050683195

0.059544219

];

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Answer 1

Star Strider 2019-2-22

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https://ww2.mathworks.cn/matlabcentral/answers/446495-making-different-length-vector-same-length#answer_362319

编辑：Star Strider 2019-2-22

在 MATLAB Online 中打开

One approach:

strainNew = interp1((1:numel(strain)), strain, linspace(1, numel(strain), numel(stress)), 'linear')';
figure
plot((1:numel(strain)), strain)
hold on
plot(linspace(1, numel(strain), numel(stress)), strainNew)
hold off

It creates a 12-element vector with the same beginning and ending values as the original vector to do the interpolation.

EDIT — Added transpose operator (') to create (12 x 1) vector,, added plot. Original code otherwise unchanged.

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KH 2019-2-22

Okay, I think we are on the same page. Thanks for all the help. I will have to evaluate which option, interpolation or extrapolation, will most accurately represent my data for this project. Thanks again!

Star Strider 2019-2-22

As always, my pleasure!

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Answer 2

Jos (10584) 2019-2-22

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https://ww2.mathworks.cn/matlabcentral/answers/446495-making-different-length-vector-same-length#answer_362315

编辑：Jos (10584) 2019-2-22

在 MATLAB Online 中打开

[EDITED] This might work for you:

ix = linspace(1, numel(stress), numel(strain))
NewStrain = interp1(ix, strain, 1:numel(stress))

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KH 2019-2-22

I believe that only gives me a [9x1], instead of the [12x1] I need for strain to be in order to match stress.

Jos (10584) 2019-2-22

I mixed up strain and stress ...

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Answer 3

KH 2019-2-22

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That is an interesting solution! I do have one question though. Because the code you provide assumes that the maximum strain value is the last one present, is it not possible to create a code that can interpolate further than this value. With this data, I am assuming the last value would be slightly greater than the last value provided, 0.0595.