how to compare two consecutive values in a matrix

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qing li 2022-7-29

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评论： qing li 2022-7-31

deal all,

how to compare two consecutive values in a matrix called 'temp' row-wise, the rule and the expecting result is as the following:

if first value>=second value , then bit=1;

else if first value<second value, then bit=0;

Store the bit generated every time in a matrix ‘M’.

This step will generate a matrix ‘M’ (logical) of size same a temp.

say for instance let's say matrix 'temp' be temp=[1,2,2,1;3,4,4,3;5,6,6,5;7,8,8,7]

can anyone give me some hints, thx a lot !

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Answer 1

Voss 2022-7-29

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https://ww2.mathworks.cn/matlabcentral/answers/1770680-how-to-compare-two-consecutive-values-in-a-matrix#answer_1017695

在 MATLAB Online 中打开

temp=[1,2,2,1;3,4,4,3;5,6,6,5;7,8,8,7]
temp = 4×4
     1     2     2     1
     3     4     4     3
     5     6     6     5
     7     8     8     7

In each row, you have one fewer comparisons than you have elements, so M is of size one less than temp.

M = logical(temp(:,1:end-1) >= temp(:,2:end))
M = 4×3 logical array
   0   1   1
   0   1   1
   0   1   1
   0   1   1

Maybe you want to append a column of false values to M.

M(:,end+1) = false
M = 4×4 logical array
   0   1   1   0
   0   1   1   0
   0   1   1   0
   0   1   1   0

Another way to do the same:

temp2 = [temp NaN(size(temp,1),1)];
M = logical(temp2(:,1:end-1) >= temp2(:,2:end))
M = 4×4 logical array
   0   1   1   0
   0   1   1   0
   0   1   1   0
   0   1   1   0

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Voss 2022-7-30

在 MATLAB Online 中打开

In that case, you can do it like this:

temp=[1,2,2,1;3,4,4,3;5,6,6,5;7,8,8,7]
temp = 4×4
     1     2     2     1
     3     4     4     3
     5     6     6     5
     7     8     8     7
% make a row vector of the elements in temp in the proper order for the comparison
temp_row = reshape(temp.',1,[]);
% add the first element to the end for comparing the last and first elements
temp_row(end+1) = temp(1);
disp(temp_row)
     1     2     2     1     3     4     4     3     5     6     6     5     7     8     8     7     1
% perform the comparison
M = temp_row(1:end-1) >= temp_row(2:end)
M = 1×16 logical array
   0   1   1   0   0   1   1   0   0   1   1   0   0   1   1   1
% reshape the result back to the right size
M = reshape(M,size(temp,2),[]).'
M = 4×4 logical array
   0   1   1   0
   0   1   1   0
   0   1   1   0
   0   1   1   1