How can I remove rows in a matrix with a range of value that I do not want?

Hi sorry if this is a simple question but I am struggling to work my script. I have a huge dataset with over 40 million points and 20 columns. One is for depth and I am trying to remove values above 6m and below 10m and only keep the rows which have a range of -10m to -6m in depth (depth is in column 4).

I have this so far but i am unsure what to do next and I am really struggling in trying to source a range of values.

clc
close all
Z=readmatrix('filename.txt');

%z = (Z>-6.0);
%z = (Z()<-10.0);
Z(Z(:,4)>-6.0) = NaN;
Z(Z(:,4)<-10.0) = NaN;
Z(any(isnan(Z),:20),:) = [];

Many thanks for any help.

Answer 1

[Walter Roberson]

depth = Z(:, 4);
mask = depth >= -10 & depth <= -6;
Z = Z(mask, :);