How to Remove Elements in a Matrix Less than a Threshold?

Hi,

I have a 3000 x 3000 matrix and want to remove all elements inside the matrix that are less than a specific value, .5 for example.

How would I go about this?

Here's what I have so far but it doesn't seem to work:

function y = highestValues(a,b)
% a is the matrix
% b is the threshold value

[sortedValues,~] = sort(a,1,'descend');
exclude = sortedValues < b;
sortedValues(exclude) = [];
highestValue = sortedValues;
clearvars n sortedValues;
y = highestValue;

Thank you!

Answer 1

[Wayne King]

You can just do this: (removing all entries larger in absolute value than 2)

x = randn(10,10);
indices = find(abs(x)>2);
x(indices) = [];

But then x will be a vector and no longer a matrix of the same size you started with:

You can also do this:

    x = randn(10,10);
    indices = find(abs(x)>2);
    x(indices) = NaN;

This will maintain your matrix.

[Image Analyst]

It should be noted that the find() is not necessary.

[Pierre Lonfat]

Do not work ! Matrix is not maintained ...

[hbabar]

Ofcourse if you remove the elements, which was what was asked in the question, the matrix will not be mantained. If you just want to replace those values with a zero just do this:

A.*(A>Threshold))

Answer 2

[Mohiuddin Ahmed]

I have a matrix like this : X =

    5.1000    3.5000
    4.9000    3.0000
    4.7000    3.2000
    4.6000    3.1000
    5.0000    3.6000
    5.4000    3.9000
    4.6000    3.4000
    5.0000    3.4000
    4.4000    2.9000
    4.9000    3.1000

I would like to delete an element from the matrix. how can I do that ?

[Image Analyst]

You can't because the matrix would no longer be rectangular if you deleted just one element. You need to delete a whole row or whole column.

X(rowToDelete,:) = []; X(:, columnToDelete) = [];

[Mohiuddin Ahmed]

well, if I want to delete an entire row from the matrix X? How can I do that ?

[Marco Noll]

%lets assume we have some time 
%and measurement data and want 
%to remove any data that is out of range

%create some sample matrix
c= [1:6;100:105]
%create a mask matrix with all 1 where criteria matches
mask = c>102 & c<105
%use the second row of the mask to remove the data columns
c(:,mask(2,:))
%should work the same when transposing it