Pairwise subtraction of rows in the same matrix

Hello guys...

Please I have this code

How can I subtract each row from all other rows(R) ... like subtracting R1-R1; R1-R2, R1-R3... R1-Rn+1 AND

then R2-R1, R2-R3.... R2-Rn+1 for all the rows

A1 = [...
     0     0     1     1     1
     0     1     1     1     1
     1     1     1     1     1
     1     1     1     1     1
     1     1     1     1     1
     0     0     1     1     1
     1     0     1     0     1
     0     0     0     0     1
     1     1     1     1     1
     1     1     1     1     1
     0     1     1     1     1
     1     0     1     0     1
     0     0     1     0     1
     1     1     1     1     1
     1     1     1     1     1
     1     0     1     1     1
     0     0     1     1     1
     0     1     1     1     1
     1     1     1     1     1];

I need this urgently....

Thanks

[per isakson]

Is the expected result one matrix of the same size as A1 ?

btw: Why your question is NOT "urgent" or an "emergency"!

[David Goodmanson]

Hi Adedeji,

In the more recent versions of Matlab the expression

A - A(:,n)

conveniently subtracts the nth column of A from each and every column of A.

[comment intended to provide an expression that could be used as a building block]

[Adedeji]

Thanks David,

However, this does not work.

Each row stands for a customer with different 5 properties (The columns).

I wish to perform a pairwise subtraction all customers from the others such that all permuations have the results of the 5 attributes each.

[Image Analyst]

Why do you need this quirky thing? Is it homework?

Have you tried diff()?

[Adedeji]

It's not a homework but part of an ongoing project of mine

as I explained while replying to David's answer.

I wish to subtract each customers 5 attributes (The Columns) from the other customers'.

The rows are the customers

The columns are their 5 attributes.

[Adedeji]

I have tried Diff()

but it's not giving me a pairwise subtraction across all possible combinations of rows there could be.

Answer 1

[madhan ravi]

Aa= reshape(a',1,size(a,2),[])- a; % a your matrix , each page of Aa represents each row’s subtraction 
A=reshape(permute(Aa,[2,1,3]),size(a,2),[]).'

[Adedeji]

Thanks all,

However, non of these work.

Each row stands for a customer with different 5 properties (The columns).

I wish to perform a pairwise subtraction all customers from the others such that all permuations have the results of the 5 attributes each.

[madhan ravi]

First you said rows now your saying columns?? Illustrate with a short 2 by 2 matrix and show how your output should look like.

[Adedeji]

My initial question actually said rows if you check. I was jsut being explicit with what they actually stand for.

FOr example, given

D =

2 3 4 5 6

4 5 2 6 7

3 5 7 3 7

I want to subtract Row1-Row1, Row1-ROw 2, Row1-Row3

Row2-Row1, Row2-Row2, Row2-Row3

Row 3-Row1, Row3-Row2, Row3-Row3

Then have them indexed such that I know which row subtraction is which result.

Thanks Ravi.....

[madhan ravi]

That's what my code does:

Wanted = reshape(D',1,size(D,2),[]) - D
% Wanted(:,:,1) - represents subtraction of first row with all the other rows und so weiter

If the above doesn't do what you want then you need to show explicitly how your output should look like.

[Adedeji]

When I tried your code, it kept flagging the error below

Error using -

Matrix dimensions must agree.

[madhan ravi]

Wanted = bsxfun(@minus,reshape(D.',1,size(D,2),[]), D) % the reason was your using version prior to 2016b, that's why when you ask a question you should fill up the field "Release" thereby these kinds of misunderstandings can be avoided

[Adedeji]

Exactly!!!!!!

This gives me what I want...

But I also want to sum all the elements for each row and divide it by 5 for all the possible combinations.

So I end up with a 3 by 3 matrix again.

Please how do you advice I do this.