Finding the first and last element of a matrix

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Sobhan 2012-5-30

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评论： Thabo Alfred Tsebe 2021-11-19

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Dear all,

I have a problem and I hope somebody can help.

I want to find the value of min, max, start and end of different columns (rows 1:50) of my matrix in a loop.

the formula below gave me the min and max as I wanted:

f = 1:nfiles
output1 (:,f)= min (mydata (1:50 (:,f),f)); 
otput2 (:,f)= max (mydata (1:50 (:,f),f));

Now how can I find the first and last element? So in my case the 1 and 50?

I hope I am clear enough.

Thanks in advance,

Sobhan

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Thabo Alfred Tsebe 2021-11-19

lin(1;end)

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Answer 1

Thomas 2012-5-30

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Suppose you have a matrix of 5 columns by 50 rows

val=rand(50,5);    % generate the data
min_val=min(val)                % min value in each column
max_val=max(val)               % max value in each column
first_ele=val(1,:)    % first value
last_ele=val(50,:)   %last value (50th)

edit

IF you donot know the position of last element use

last_ele=val(end,:) %last value

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Sobhan 2012-5-30

Dear Thomas,

Thanks for your answer. I forgot to say something: the rows that I am interested in (in my example 1:50) changes throughout the loop. For example for one file is 1:30 and for another one is 1:15.

I want a kind of solution that find the first and last element regardless my indexing range. Finding the min and max was easy but first and last element no!

cheers

Thomas 2012-5-30

check my edit..

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Answer 2

Nurye Hassen 2017-11-23

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The first element is obvious.i.e. A(1,1) gives you the first elemnt of A. But for the last one, When ever the loop changes you can ask the new number of the row and its respective value. Here is an example..Inside the loop write... For matrix A

rows=size(A,1); Value=A(rows,end);