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Write a function called minimax that takes M, a matrix input argument and returns mmr, a row vector containing the absolute values of the difference between the maximum and minimum valued elements in each row. As a second output argument called mmm,

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Debaditya Chakraborty
Debaditya Chakraborty on 27 May 2019
Closed: Rik on 24 Jul 2020
Write a function called minimax that takes M, a matrix input argument and returns mmr, a row vector containing the absolute values of the difference between the maximum and minimum valued elements in each row. As a second output argument called mmm, it provides the difference between the maximum and minimum element in the entire matrix. See the code below for an example:
>> A = randi(100,3,4) %EXAMPLE
A =
66 94 75 18
4 68 40 71
85 76 66 4
>> [x, y] = minimax(A)
x =
76 67 81
y =
90
%end example
%calling code: [mmr, mmm] = minimax([1:4;5:8;9:12])
Is my logic correct?
my approach
function [a,b]= minimax(M)
m=M([1:end,0);
a= [abs(max(M(m))-min(M(m)))];
b= max(M(:)) - min(M(:));
end

  15 Comments

Rik
Rik on 11 Jun 2020
My reason for closing this question: people are just posting their answers to this homework question, without substantial discussion happening. Once there is an option to disallow new answers while allowing comments that option should be considered for this thread.

Answers (15)

mayank ghugretkar
mayank ghugretkar on 5 Jun 2019
here's my function....
went a little descriptive for good understanding to readers.
function [a,b]=minimax(M)
row_max=max(M');
overall_max=max(row_max);
row_min=min(M');
overall_min=min(row_min);
a=row_max - row_min;
b=overall_max-overall_min;
Code to call your function
[mmr, mmm] = minimax([1:4;5:8;9:12])

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Rik
Rik on 12 Jun 2019
Because the min function operates only in one direction. If you want it to operate along a different direction, you can either transpose the matrix (as Mayank has done), or use the third input, as described in the documentation (which I would suggest).
Purushottam Shrestha
Purushottam Shrestha on 8 Jun 2020
We need to transpose because max(M.') gives a row vector of maximum elements of each row. I want you to try by giving command >>max(A.') Then you can see clearly.
Stephen Cobeldick
Stephen Cobeldick on 17 Jul 2020
"We need to transpose because max(M.') gives a row vector of maximum elements of each row."
In some specific cases it will, but in general it does not.
"I want you to try by giving command >>max(A.') Then you can see clearly."
Okay, lets take a look:
>> A = [1;2;3]
A =
1
2
3
>> max(A.')
ans = 3
I can clearly see that this does NOT give the maximum of each row of A.

kannan vidyadhar
kannan vidyadhar on 29 Apr 2020
Edited: kannan vidyadhar on 29 Apr 2020
this is how i did
function [mmr,mmm]=minimax(A)
mmt=[max(A,[],2)-min(A,[],2)];
mmr=mmt'
mmm=max(A,[],"all")-min(A,[],"all")

  3 Comments

Kailash Ramasubramaniam
Kailash Ramasubramaniam on 9 May 2020
function [mmr,mmm]=minimax(r)
mmr= [max(r(1,[1:end]))- min(r(1,[1:end])),max(r(2,[1:end]))- min(r(2,[1:end])),...
max(r(3,[1:end]))- min(r(3,[1:end]))];
mmm=max(r(:))-min(r(:));
end
This the code which I wrote for this question. This works fine for matrices till 3 rows,after which it fails. I am new to matlab. Can someone help me to correct this code for random matrices please?

Arooba Ijaz
Arooba Ijaz on 1 May 2020
function [mmr,mmm] =minimax (M)
%finding mmr
a=M'
b=max(a)
c=min(a)
mmr=b-c
%finding mmm
d=max(M)
e=max(d)
f=min(M)
g=min(f)
mmm=e-g

  3 Comments

Walter Roberson
Walter Roberson on 9 Jun 2020
M is two dimensional. When you take max() of a two-dimensional matrix, then by default the maximum is taken for each column, so you would go from an m x n matrix to a 1 x n matrix of output. Then max() applied to that 1 x n matrix would take the maximum of those values, giving you a 1 x 1 result.
Rik
Rik on 9 Jun 2020
This is done, because max only operates on a single dimension. Starting from R2018b you can specify a vector of dimensions, or use the 'all' keyword, see the documentation. In this answer they probably should have written max(M(:)) instead. I don't know who upvoted this function, as it is undocumented and takes a strange path to an answer.

Nisheeth Ranjan
Nisheeth Ranjan on 28 May 2020
function [mmr,mmm]=minimax(A)
mmt=[max(A,[],2)-min(A,[],2)];
mmr=mmt'
mmm=max(max(A))-min(min(A))
This is the easiest code you cold ever find. Thank me later.

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Geoff Hayes
Geoff Hayes on 27 May 2019
Edited: Geoff Hayes on 27 May 2019
Is my logic correct?
I'm not clear on why you need the m. In fact, doesn't the line of code
m=M([1:end,0);
fail since there is no closing square bracket? What is the intent of this line?
Take a look at max and min and in particular the "dimension to operate along" parameter and see how that can be used to find the minimum and maximum value in each row (as opposed to in each column).

  4 Comments

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Geoff Hayes
Geoff Hayes on 28 May 2019
how can I assign each row to this function one after the other?
I don't understand your question. Why do you need to assign each row to this function? If you do
>> min(A, [], 2)
then that will return a vector/array with the minimum value in each row of A...
Sahil Deshpande
Sahil Deshpande on 30 May 2020
function [mmr,mmm] = minimax(M)
mmr = abs(max(M.')-min(M.'));
mmm = max(max(M)) - min(min(M));
I did it this way

pradeep kumar
pradeep kumar on 26 Feb 2020
function [mmr,mmm]=minimax(M)
mmr=abs(max(M')-min(M'));
mmm=(max(max(M'))-min(min(M')))
end

  1 Comment

Rik
Rik on 26 Feb 2020
Why would you use the transpose if you can also simply use the third input argument for min?
Also, max(max(M')) is equivalent to max(max(M)) and max(M(:)) (and also to max(M,[],'all'), so you could even use that).

Rohan Singla
Rohan Singla on 17 Apr 2020
function [mmr,mmm] = minimax(M)
a=M';
mmr=max(a,[],1)-min(a,[],1);
mmm= max(M(:)) - min(M(:));
end

  5 Comments

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Walter Roberson
Walter Roberson on 12 May 2020
M' is conjugate transpose. Unless you are doing specialized linear algebra, it is recommended that you use .' instead of ' as .' is regular (non-conjugate) transpose.

AYUSH MISHRA
AYUSH MISHRA on 26 May 2020
function [mmr,mmm]=minimax(M)
mmr=max(M')-min(M');
mmm=max(max(M'))-min(min(M'));
end
% here M' is use because when we are using M than mmr generate column matrix
SOLUTION
[mmr, mmm] = minimax([1:4;5:8;9:12])
mmr =
3 3 3
mmm =
11

Anurag Verma
Anurag Verma on 26 May 2020
function [mmr,mmm]=minimax(M)
a = max(M(1,:))-min(M(1,:));
b = max(M(2,:))- min(M(2,:));
c = max(M(3,:))- min(M(3,:));
mmr = [a,b,c];
mmm = max(M(:))-min(M(:));
what's wrong with this code. can anyone explain please it gives an error with the random matrix question?

  2 Comments

Rik
Rik on 26 May 2020
Your code will only consider the first 3 rows. It will error for arrays that don't have 3 rows, and will return an incorrect result for arrays that have more than 3 rows.
You should read the documentation for max and min, and look through the other solutions on this thread for other possible strategies to solve this assignment.
saurav Tiwari
saurav Tiwari on 11 Jun 2020
yaa, RIK is right. your code can only work for 3 rows matrix but random matrix contain a matrix of rows>1 . ok so, you should have to make a code that can work for any type of matrix

Md Naim
Md Naim on 30 May 2020
function [mmr, mmm]= minimax(M)
mmr = max(M')-min(M')
mmm = max(max(M'))-min(min(M'))
end

  0 Comments


ROHAN SUTRADHAR
ROHAN SUTRADHAR on 6 Jun 2020
function [mmr,mmm] = minimax(A)
X = A';
mmr = max(X([1:end],[1:end]))- min(X([1:end],[1:end]));
mmm = max(X(:))-min(X(:));
end

  0 Comments




Akinola Tomiwa
Akinola Tomiwa on 23 Jul 2020
Function [mmr, mmm] = minmax(x)
mmr = (max(x, [], 2) - min(x, [], 2)';
%the prime converts it to a row matrix
mmm = (max(x(:)) - min(x(:));
end

  4 Comments

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Akinola Tomiwa
Akinola Tomiwa on 23 Jul 2020
Oh, alright, thanks I'll do well to write codes in smaller piece. Thanks a lot
Function [mmr, mmm] = minimax(x)
min_value = min(x,[], 2); % this takes the row minimum values of the supplied matrix
max_value = max(x, [],2); % this takes the row maximum values
mmr = (max_value-min_value)'; % the prime converts the colon to a row
mmm = (max(x(:)) - min(x(:)) ;
%x(:) converts the matrix to a single colon matrix so max(x(:)) returns a single value the maximum value
end
How is this ?
Walter Roberson
Walter Roberson on 23 Jul 2020
mmm = (max(x(:)) - min(x(:)) ;
1 2 3 21 2 3 21
The number indicates the bracket nesting level in effect "after" the corresponding character. You can see that you have one open bracket in effect at the end of the line.
youssef boudhaouia
youssef boudhaouia on 24 Jul 2020
function [mmr,mmm]=minimax(M)
a=M';
ma=max(a);
mi=min(a);
mmr = ma - mi ;
mmm=max(max(M)) - min(min(M));
end
Here's my answer, as simple as possible and it works.

youssef boudhaouia
youssef boudhaouia on 24 Jul 2020
function [mmr,mmm]=minimax(M)
a=M';
ma=max(a);
mi=min(a);
mmr = ma - mi ;
mmm=max(max(M)) - min(min(M));
end
here's my answer as simple as possible , it works!

  0 Comments

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