get the minimum and maximum element from two vectors.

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Shuoze Xu
Shuoze Xu 2022-4-8
评论： Shuoze Xu 2022-4-8
Hi.
That is question.
Write a MATLAB function called minMaxVectors that takes two vectors v1 and v2 (you can assume these vectors have the same length) as its parameters and returns two values: the minimum of both of these vectors, and the maximum of both of these vectors. You must also write a driver file called minMaxVectorsDriver to test your program.
Testing
Your driver program should embed test cases and print the results returned by minMaxVectors. Some example test cases are:
input1 input 2 min max
[ 1 2 ] [ 3 4 ] 1 4
[ 5 ] [ -5 ] -5 5
[ 1 9 ] [ 5 6 ] 1 9
That is my code
% That is function file
function [d1 d2] = minMaxVectors(v1,v2)
n1 = 0;
n2 = 0;
for i = 1:length(v1)
if n1 > v1(i) % if the number of min is bigger than v1
n1 = v1(i); % let min is equal to the elements of v1
d1 = n1;
end
end
for i = 1:length(v2)
if n2 < v2(i) % if the number of min is smaller than v2
n2 = v2(i); % let max is equal to the elements of v2
d2 = n2;
end
end
if n1 < n2
d1 = n1;
end
end
That is test file
% set two vector, first vector elements are 1 4,
% second vector elements are 4 -1
v1 = [1 4];
v2 = [4 -1];
[num1 num2] = minMaxVectors(v1,v2);
disp([num1 num2]);
On my code, it cannot be get the minimum element by comparing two vectors
The output is 0 4
How to improve my code?
Thank you all.

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采纳的回答

Davide Masiello
Davide Masiello 2022-4-8
编辑：Davide Masiello 2022-4-8
Ran in:
You could use the min and max MatLab inbuilt functions.
v1 = [1 4];
v2 = [4 -1];
[num1 num2] = minMaxVectors(v1,v2);
disp([num1 num2])
-1 4
function [minval maxval] = minMaxVectors(v1,v2)
minval = min([v1,v2]);
maxval = max([v1,v2]);
end

更多回答（1 个）

Riccardo Scorretti
Dear Shouze, as your question looks like an assignment I'll provide only some hints, but I will not write any code in your place; I'm sure you will understand.
  1. To begin with, your algorithm has a weak point: you initializes n1 = n2 = 0. This is an error, which is likely to produce a wrong result: you should initialize them as n1 = inf and n2 = -inf if you want to obtain the correct result.
  2. Concerning names, when you read a program you must be able to tell which is the meaning of each variable (as much as possible, of course). In your case, the names n1 and n2 are meaningless: try to use something like minval instead of n1, and maxval instead of n2: your program will be much more readable.
  3. You could initialise n1 = n2 = v1(1) and start the first loop (and the first only!) from i = 2.
  4. Never use i and j as names of variables: it may be confounded with the imaginary unit 1i - expecially if you program in Matlab. Avoid also the variable l (= "letter L") because it can be easily misread as 1 (= "one") or | (= "or operator").
  5. You don't need the variables d1 and d2: just use n1 and n2.
  6. Last but not least, you wrote an algorithm in "C-style". In Matlab it would be much more effective to create a matrix the columns of which are the two vectors v1 and v2 (for instance by using mat = [v1(:) v2(:)]; the symbols (:) are required to ensure that v1(:) and v2(:) are column-vectors) then use the functions min and max (read the doc to know how).
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Riccardo Scorretti
Riccardo Scorretti 2022-4-8
Sure. inf = infinity. In your code, n1 = best candidate for the minimum. At the beginning of your algorithm, you should
  • either initialize n1 with v1(1) (assuming that v1 is not empty, otherwise you'll get an error) because min(v1) <= v1(1),
  • or n1 = inf because of course min(v1) <= inf.
If you initialize n1 = 0, you are implicitly assuming that min(v1) <= 0, which is likely to be wrong, and hence it will produce a wrong result. Even if you have specific a priori information on your data (= you are sure that min(v1) < 0), this is an extremely bad programming practice, and should be avoided in any case.
Shuoze Xu
Shuoze Xu 2022-4-8
I understand, and i have done that by using for loop.
Thanks for your help.

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