Seperate rows in matrix based on values of the elements.

Hi,

I have simplified my 'multiple radar' problem into this: Lets say I have matrix A, consisting of columns 1 (timestamp) and 2 (value). I want obtain matrices that have ascending timestamps and the difference between the values in column 2 of the new vectors must not be greater than 5.

%Input matrix [timestamp values]
A= [0   100;
    0   400;
    0   500;
    1   103;
    1   397;
    1   502;
    2   506;
    2   104;
    2   399];
%Now magic happens
%Output matrices per radar [timestamp values]
OUT1=   [0 100;
        1   103;
        2   104];
OUT2=   [0  400;
        1   397;
        2   399];
OUT3=   [0  500;
        1   502;
        2   506];    

Hopefully somebody can help me out of this misery

Answer 1

[KALYAN ACHARJYA]

for i=1:length(unique(A(:,1)))
mat{i}=A(A(:,1)==i-1,:);
end
result=cell2mat(mat)
out1=reshape(result(1,:),[2,3])' % Use loop for 3 statements
out2=reshape(result(2,:),[2,3])'
out3=reshape(result(3,:),[2,3])'

# This may be possible without loop also, recomended

[Mike Mierlo van]

I get the following error:

Error using reshape

To RESHAPE the number of elements must not change.

Error in [file] (line 15)

out1=reshape(result(1,:),[2,3])' % Use loop for 3 statements

What is the fix for this?

[Stephen23]

Note: the requirement "..the difference between the values in column 2 of the new vectors must not be greater than 5" is not checked or ensured by this answer.

[Mike Mierlo van]

Indeed.

So I am still in need of a solution for:

• the 'RESHAPE' error and

• the requirement that the difference in advancing indexes of column 2 must not be greater than 5.

Thanks in advance!

[KALYAN ACHARJYA]

I run the code with the "A" example as you provided in the question

A= [0   100;
    0   400;
    0   500;
    1   103;
    1   397;
    1   502;
    2   506;
    2   104;
    2   399];
for i=1:length(unique(A(:,1)))
mat{i}=A(A(:,1)==i-1,:);
end
result=cell2mat(mat)
out1=reshape(result(1,:),[2,3])' % Use loop for 3 statements
out2=reshape(result(2,:),[2,3])'
out3=reshape(result(3,:),[2,3])'

Command Window

out1 =
     0   100
     1   103
     2   506
out2 =
     0   400
     1   397
     2   104
out3 =
     0   500
     1   502
     2   399

Please do minor change as per new test data requirements.

[Mike Mierlo van]

Thank you! Now I get the same output. But the output matrices do still not meet the requirement:

• the difference in advancing indexes of column 2 must not be greater than 5.

Any solution for this part?

[Mike Mierlo van]

Found it myself. result=sort(result) will do the job.

Thanks for the help!!!