Automatically identify two numbers within an matrix

Is there any way to automatically locate two numbers within a matrix?

For example:

• for the file "matrix_1.txt" I am interested in identifying the following numbers 194 (min) and 201 (max)
• for the file "matrix.txt" I am interested in identifying the following numbers 175 (min) and 199 (max)

So I am interested in a code that can identify these numbers without me knowing them. Like the max/min command that identifies the max/min within a matrix for example.

[Antonios Dougalis]

Hi Alberto, I am not sure if I have understood entirely your question.

If you are looking for any number in your array use the command 'find'. It uses logical indexing to identify the linear index of the number you want

e.g.,

if your matrix above is called A the following line will result the positional index of the the value your are seeking

result_min = find(A==175);

you can then convert it to array subscript with the command ind2sub

[row,col]=ind2sub(size(A),result_min)

[Alberto Acri]

No, because the values I reported I have not known. So if I have matrix_1, I want to get as output the values 194 and 201.

[Stephen23]

@Alberto Acri: apparently you do not want to consider small values in the matrices, e.g. 0, 1, 7, 11.

What is the limit for considering or ignoring the small values?

[Alberto Acri]

Definitely ignore numbers smaller than 70.

[John D'Errico]

You are not telling us enough information. You want to find a number, like the max and min, But they may not be the smallest or largest numbers in the matrix. In fact, they are not even close to that.

So apparently you know what you want, but cannot describe it. And the matrices you show are not at all clear in how you would decide on those specific values.

Answer 1

[Voss]

matrix = readmatrix('matrix.txt');
matrix_1 = readmatrix('matrix_1.txt');

min_matrix = min(matrix(matrix >= 70))

min_matrix = 174

max_matrix = max(matrix(matrix >= 70))

max_matrix = 199

min_matrix_1 = min(matrix_1(matrix_1 >= 70))

min_matrix_1 = 194

max_matrix_1 = max(matrix_1(matrix_1 >= 70))

max_matrix_1 = 201

Answer 2

[Mathieu NOE]

hello Alberto

welcome back !

here a demo for the 'matrix.txt' case

the other one is basically the same , simply change the min / max values

 M = readmatrix('matrix.txt');
 
 value_min = 175;
 value_max = 199;
 
ind = find(M>=value_min & M<=value_max); % linear index 
 M(ind)  % show the M values (to double check)
 [r,c] = ind2sub(size(M),ind) % show corresponding row / col indexes