# How to get the rows and columns from a matrix which do not fall into particular criteria?

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Zhou Ci on 16 Mar 2023
Commented: Dyuman Joshi on 16 Mar 2023
Hello,
My data comprises of a matrix.
% Data1 = 25000 x 30 double
After running some lines of code I got my Data2 (from Data1 using logical indexing etc) which is now
% Data2 = 10000 x 30 double
However I also want to do some statistics on the rest 15000 x 30 dataset. I guess it's quite simple but I can't figure out how to get this 15000 x 30 matrix from Data1. After doing logical indexing etc I got Data2, how to get the remaining matrix which do not fall into my particular criteria for Data2 i.e, 15000x30? Thank you

Dyuman Joshi on 16 Mar 2023
Use negation on the logical indexing -
x = 0:0.01:10;
y = [sin(x); cos(x)];
%Get columns of y in which
%first row is less than or equal to -0.25
idx = y(1,:)<=-0.25;
data1 = y(:,idx)
data1 = 2×297
-0.2555 -0.2652 -0.2748 -0.2844 -0.2940 -0.3035 -0.3131 -0.3225 -0.3320 -0.3414 -0.3508 -0.3601 -0.3694 -0.3787 -0.3880 -0.3971 -0.4063 -0.4154 -0.4245 -0.4335 -0.4425 -0.4515 -0.4604 -0.4692 -0.4780 -0.4868 -0.4955 -0.5042 -0.5128 -0.5213 -0.9668 -0.9642 -0.9615 -0.9587 -0.9558 -0.9528 -0.9497 -0.9466 -0.9433 -0.9399 -0.9365 -0.9329 -0.9293 -0.9255 -0.9217 -0.9178 -0.9137 -0.9096 -0.9054 -0.9011 -0.8968 -0.8923 -0.8877 -0.8831 -0.8783 -0.8735 -0.8686 -0.8636 -0.8585 -0.8534
%Get the data which doesn't fall into that category
data = y(:,~idx)
data = 2×704
0 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600 0.0699 0.0799 0.0899 0.0998 0.1098 0.1197 0.1296 0.1395 0.1494 0.1593 0.1692 0.1790 0.1889 0.1987 0.2085 0.2182 0.2280 0.2377 0.2474 0.2571 0.2667 0.2764 0.2860 1.0000 1.0000 0.9998 0.9996 0.9992 0.9988 0.9982 0.9976 0.9968 0.9960 0.9950 0.9940 0.9928 0.9916 0.9902 0.9888 0.9872 0.9856 0.9838 0.9820 0.9801 0.9780 0.9759 0.9737 0.9713 0.9689 0.9664 0.9638 0.9611 0.9582
Dyuman Joshi on 16 Mar 2023
Lat=Data1(:,1);
Lon=Data1(:,2);
land_flags = zeros(length(Lat),1);
for i = 1 : size(land,1)
Lat_land = land(i).Lat;
Lon_land = land(i).Lon;
in1 = inpolygon(Lat(:),Lon(:),Lat_land,Lon_land);
land_flags = land_flags + in1;
end
idx = land_flags == 0:
Data1 = Data1(idx,:);
Data2 = real(Data1); % 10000x30
Data3 = Data1(~idx,:)