Given a column matrix of numbers, how to extract some numbers that meet some condition and save them in a new matrix, if I don't know how many numbers will meet the condition?

Suppose I have a matrix R of n rows and 1 column, suppose I want to extract all numbers from matrix R that are less than or equal to 0.8 and put them in a new matrix M

the thing is I don't know how many numbers of R will meet the criteria so that I can pre-define a matrix M of zeros and replace the zeros with the new numbers that meet the criteria

Answer 1

[Image Analyst]

Try

rowsToExtract = R < 0.8
M = R(rowsToExtract);

This is very very basic. Since you don't know this yet, you should probably do the 2 hours on ramp training: MATLAB Academy