Simulink error: The data abscissae must be distinct and strictly monotonic.

Question

KostasK 2019-10-17

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https://ww2.mathworks.cn/matlabcentral/answers/485916-simulink-error-the-data-abscissae-must-be-distinct-and-strictly-monotonic

编辑： KostasK 2019-10-17

Hi all,

I have constructed a simulink model, where within the model I have a MATLAB function block as you can see. Within that block, a very simple code loads data from a .mat file and interpolates using interp1.

However I get the following error when I run the model which I have managed to trace to the line in the MATLAB function block where the interpolation occurs:

An error occurred while running the simulation and the simulation was terminated

Caused by:

The data abscissae must be distinct and strictly monotonic.

Component:Simulink | Category:Block error

This is simple enough, as one would assume that my x vector in the interp1 function includes non-monotonic data. But the problem is that it doesn't! I have tested that by running the code in the MATLAB function block by itself as a normal matlab file, and also used unique to tripple check and it works perfectly. I also checked where the current folder to ensure that the file is taken from the right place. So I really do not know why the interp1 function presents this problem when I am running it in Simulink. It must be something that I don't understand.

Any suggestions?

Kind Regards,

KMT.

P.S. Attached you can find the files that I am using. Just download and run if you need to.

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Answer 1

Daniel M 2019-10-17

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https://ww2.mathworks.cn/matlabcentral/answers/485916-simulink-error-the-data-abscissae-must-be-distinct-and-strictly-monotonic#answer_396858

编辑：Daniel M 2019-10-17

在 MATLAB Online 中打开

None of the variables in the matfile are monotonic.

all(sign(diff(Tga))==1) % ans = 0
all(sign(diff(Tm1))==1) % ans = 0
all(sign(diff(Tm2))==1) % ans = 0
all(sign(diff(thx))==1) % ans = 0
x = -10:10;
all(sign(diff(x))==1) % ans = 1

Perhaps try unwrap, as the values of thx seem to be between -pi and pi.

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Daniel M 2019-10-17

在 MATLAB Online 中打开

I have solved it. If you unwrap thx such that it become monotonic, now there is a duplicate! It occurs because thx has entries for 3.1416 and -3.1416 (and unwrapped they become the same). So I removed the second entry.

Add this code to your matlab function after you load the data:

thx(201) = [];
Tga(201) = [];
thx = unwrap(thx);

And this function shouldn't have any more problems. And the simulink program generates an error further along the simulation (hey... it's still progress!).

KostasK 2019-10-17