why do I get this error?

Hey Thats the code I put and the error:

time1 = AIS1(:,end-4:end)

Index in position 2 is invalid. Array indices must be positive integers or logical values.

Could anybody tell me why?

Answer 1

[Image Analyst]

AIS1 has 4 or fewer columns.

s = size(AIS1)

[flashpode]

well that was not the problem I did it another way

thank you

[Image Analyst]

For index 2 to be invalid, it means that end-4 is either 0 or negative. It could be 0 if there were exactly 4 columns in AIS1. It would be negative if AIS1 had only 1, 2, or 3 columns. I'm very sure, from the error you gave, that having 4 or fewer columns was the problem. If it weren't, you would not have gotten that error, you would have gotten no error at all, or would have gotten a different error.

https://matlab.fandom.com/wiki/FAQ#.22Subscript_indices_must_either_be_real_positive_integers_or_logicals..22

Anyway, I'm glad it's working and thanks for Accepting the Answer.

[flashpode]

Ah, okay. What I posted was to get the last four digits of each row of the string

[Image Analyst]

If AIS1 is a simple string or character array, you'd do AIS1(end-4:end). If it's an array of strings, say 100 of them, and you wanted only the last 4 characters off each of them in a new 100 element long string where each string is only 4 characters one way is to do this:

% Make an array of strings.
AIS1 = ["1234567", "123456789"]
for k = 1 : numel(AIS1)
	% Get this string as a character array.
	thisString = char(AIS1(k));
	% Get the last 4 characters of this string
	% and put into the k'th cell of a cell array.
	last4{k} = thisString(end-4:end);
end
% last4 is a cell array where each cell is a character array.
% Convert to a string array if desired:
last4 = string(last4)