How to find an array in a vector or matrix?

I want to find a specific number in a vector, and I am using the following command

[s,t] = find(q_p_d100==qp100max)

But I get the follwoing:

s =

0×1 empty double column vector

t =

0×1 empty double column vector

However, I simply need a raw and column number of the position of the number I'm looking for.

('qp100max' is the maximum number in 'q_p_d100 vector')

Answer 1

[Jan]

The output of FIND shows you, that qp100max is not the maximum value of q_p_d100, but it is not even an element of the vector:

any(q_p_d100 == qp100max)   % FALSE

I assume, this is a rounding problem. Try it:

max(q_p_d100) - qp100max

Is this a small value?

To get the position of the maximum value:

[maxV, index] = max(q_p_d100)

If the value is not unique:

allIndex = find(q_p_d100 == maxV)

Answer 2

[Ahmed Redissi]

You can use the function "ismember" to find if an array or a scalar is part of another array. Here is the documentation for it so you can learn how to use it:

https://www.mathworks.com/help/matlab/ref/double.ismember.html