# Finding indices of certain numbers from simulation data

3 views (last 30 days)
Abhinav Aravind on 1 Mar 2023
Commented: Abhinav Aravind on 8 Mar 2023
Hello all,
I want to find out the index values of certain numbers from an array dataset obtained from a Simulink simulation. The simulation results are stored in the workspace as an array. I am logging it to the workspace using a scope.
I tried using the find() command to find the index values, but it just returned an empty vector. I even tried using ismember() to return 0 or 1 based on whether a number belongs to that simulation data, but that also returned an empty vector.
The find() command works fine when using it on arrays imported from excel sheet.
I am not sure what I am doing wrong. Any suggestions or advice would be of great help. Thank you very much in advance.
Edit: I have attached the simulation file
Askic V on 5 Mar 2023
Edited: Askic V on 6 Mar 2023
Is it possible that array is of type double (all elements are double) and you try to use the function find to find this specific number?
It is very hard to use "equal" with double numbers because there is no infinite precision
x = [1, 1/3, 3/4, 4/5, 1, 1.1]
x = 1×6
1.0000 0.3333 0.7500 0.8000 1.0000 1.1000
[c, i] = find(x==0.333333333333333)
c = 1×0 empty double row vector i = 1×0 empty double row vector

Akira Agata on 6 Mar 2023
The following is an example:
x = [1, 1/3, 3/4, 4/5, 1, 1.1];
idx = ismembertol(x, 0.33, 0.01); % find 0.33±max(x)*0.01
idx
idx = 1×6 logical array
0 1 0 0 0 0
x(idx)
ans = 0.3333
Abhinav Aravind on 8 Mar 2023
Thank you Akira for the suggestion.
I tried this method. Although the required number shows up, I am unable to find the index of that number. Perhaps, could you suggest a way of finding the index of that as well ?
Thank you once again

Sarvesh Kale on 6 Mar 2023
Suppose your logged data is x in workspace then to find index of a certain number in that you can do the following
x=[1,1,1,2,2,3,3,4,5,5,5];
n=1:length(x) % generate index vector
n = 1×11
1 2 3 4 5 6 7 8 9 10 11
key = 2 ;
idx = x == key % comparision to search your number
idx = 1×11 logical array
0 0 0 1 1 0 0 0 0 0 0
n(idx) % this will give you index
ans = 1×2
4 5
I hope this helps
Thank you
Abhinav Aravind on 8 Mar 2023
Thank you very much for the suggestion, Sarvesh Kale. I tried this method, it works fine with integers but not with float values.
The array generated from the simulation does not contain pure integers, but decimal values.

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