I have a 9x1253 matrix: i found the max values of this matrix, but i need to find what row and column they belong to and show that.

gasoline is a matfile of a 9x1253 matrix

this code is what i used to find the max values of the matrix

i started from 2 becuase the first row and column where names and not values.

gasoline

a=gasoline(2:end,2:end)

b=cell2mat(a)

c=max(b)

my question is how do i find the location of the max values in the original matrix gasoline in order to display the date for the column and row it occurs in.

Answer 1

[per isakson]

See the subsection Largest Element in Matrix of

https://se.mathworks.com/help/matlab/ref/max.html

In response to comment:

This is close to the example in the documentation

%% 
A = randn( 9, 1253 ); % sample data
%%
[ M, ix ] = max(A(:));
[ ixr, ixc ] = ind2sub( size(A), ix );
%%
M, ixr, ixc

returns

M =
    3.5699
ixr =
     5
ixc =
   164   
   

One has to follow the examples in the documention in detail. Similar isn't good enough.

[Matthew Weathersby]

i used similar code to the one in the largest element in matrix subsection. it only shows those 8 values of the max that i found in its own array. for instance when i find row and column these max values are in, it only says 1,2,3,4,5,6,7,8. instead of finding the max value in the 1253x9 matrix. I went on excel and found the max values by hand, but there has to be some function that can find the max value of those 8 values in the 1253x9 matrix. please let me know if i am making sense. this is my code so far.

gasoline

a=gasoline(2:end,2:end)

b=cell2mat(a)

c=max(b)

c returns a 1x8 matrix with the max values, i need to find these values in the 1253x9 matrix

[Matthew Weathersby]

thank you so much for the response!

i was reading the question wrong. it wanted to max value of the max values.

I used this as my code:

a=gasoline(2:end,2:end)

b=cell2mat(a)

c=max(b)

d=max(max(b))

[row,col]=find(b==4.57)

gasoline{933+1}

So, i found that in row 8 column 933 is where the max value is, but i did not include row 1 column 1 because they are names not values.

i added one to the column number to take into consideration in the original array there is a column full of names to row 9.

this led me to believe the actual value was in column 933+1 for the column not included.

Thanks for the feed back

[per isakson]

The code based on the example of the documentation will give the same result and it's faster.

find(b==4.57) may give the wrong result because of floating point error. See https://se.mathworks.com/matlabcentral/answers/41877-matlab-floating-point-errors#answer_51565