Getting/sorting by range of numbers - syntax issue

Question

I'm using octave and I'm having trouble sorting out a range. I can do the delta section by just saying include anything less than or equal to 4. But I forget how to select a range of numbers for the Theta section. example from 4 to 8.

PS I'm using Octave/Matlab

%   delta 0hz to 4 hz
    array2_deltafreq_sort=sortrows(array2,1); %used only to export txt file
    array2_deltafreq_sort_limit_idx=array2_deltafreq_sort(:,1)<=4 ;% idx to limit array 

I tired

%theta 4hz to 8hz
    array2_thetafreq_sort=sortrows(array2,1); %used only to export txt file
    array2_thetafreq_sort_limit_idx=array2_thetafreq_sort(:,1)<=4 & array2_thetafreq_sort(:,1)>=8  ;% idx to limit array to
    array2_thetafreq_sort_limit=array2_thetafreq_sort(array2_thetafreq_sort_limit_idx,:);

but when I look at the array I get array2_thetafreq_sort_limit = [](0x8)

Answer 1

尝试这个：

    array2_thetafreq_sort_limit_idx=array2_thetafreq_sort(:,1)<=8 & array2_thetafreq_sort(:,1)>=4  ;% idx to limit array