How to set an upper and lower limit on a data set from a matrix

I need to set an upper and lower limit on the numbers in a data set that belongs to a matrix.

How would I go about doing this?

[James Tursa]

Please provide a short example showing inputs and desired output.

[jgillis16]

I have a data set that goes from 0 to 360 that is apart of a matrix called GalList >>> GalList(:,3). I need to extract values ranging only from 176.71 to 198.71.

Answer 1

[Walter Roberson]

at_least = -5.1234;   %for example
at_most = 308.42;     %for example
new_matrix = min(max(YourMatrix, at_least), at_most);

Now new_matrix has had every value less than at_least replaced with at_least, and every value greater than at_most replaced with at_most.

Answer 2

[James Tursa]

Assuming you want to extract all the rows where the 3rd column meets your conditions:

GalList = your matrix
lower_limit = 176.71;
upper_limit = 198.71;
x = (GalList(:,3) >= lower_limit) & (GalList(:,3) <= upper_limit);
extracted_rows = GalList(x,:);

[jgillis16]

Great! This was exactly what I was looking for!

From this, would you know how to possible extract the lines (from the text file) that the extracted numbers in column 3 correlate with?

[James Tursa]

Do you mean read in only those lines, or create a new file with only those lines, or what? How are you currently reading this file?

[jgillis16]

Currently, my code looks like the following:

load virgoclusterrm.txt %loads text into workspace
readCatalog( virgoclusterrm )
fid = fopen( 'virgoclusterrm.txt');
trashLine = fgets(fid); %Skips the first line
data = textscan(fid, '%f%s%f%f%s%f%f%f%f%f%f%f%f%f%f%f%f%f', 'Delimiter', '|', 'TreatAsEmpty','~');
fclose(fid);
GalList.pgc = data{1};
GalList.name = data{2};
GalList.ra = data{3};
RA = GalList.ra.*15;
GalList.dec = data{4};
GalList.major = data{7};
GalList.abs_mag = data{14};
GalList.dist = data{15};

lower_limit = 176.71;
upper_limit = 198.71;
x = (RA >= lower_limit) & (RA <= upper_limit);
extracted_rows = RA(x,:);

RAo = extracted_rows./15;

RAo contains the values I restricted column 3 to. But, column 3 was originally derived from the text file, virgoclusterrm.txt. Now, I have these 877 values but I want to correlate them back to their respective lines of text.

Would there be any way to scan the original text file for the values in RAo in column three, and extract any matches into a new text file?