Conditional statement in random integers to classify

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SeungHyun Cha 2020-4-14

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https://ww2.mathworks.cn/matlabcentral/answers/517715-conditional-statement-in-random-integers-to-classify

评论： Ameer Hamza 2020-4-14

for Vector = randi([0 99],10000,1)
if Vector (Vector >= 0 & Vector <= 24)
    range0to24 = length(find(Vector>=0 & Vector<=24))
elseif Vector (Vector >= 25 & Vector <= 49)
    range25to49 = length(find(Vector>=25 & Vector<=49))
elseif Vector (Vector >= 50 & Vector <= 74)
    range50to74 = length(find(Vector>=50 & Vector<=74))
elseif Vector (Vector >= 75 & Vector <= 99);
    range75to99 = length(find(Vector>=75 & Vector<=99))
end
end

I want to make conditional statements that classify random integer numbers in the range of 0 to 99.

I think actually, Vector is a 10000 X 1 column vector, so I think above codes should be worked.

However, it shows only range25to49 even though, there is no difference between other range codes.

I do not understand why other ranges are not shown. Please help me ㅠㅠ

P.S. I must use only for-loop and conditional statements.

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Answer 1

Ameer Hamza 2020-4-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517715-conditional-statement-in-random-integers-to-classify#answer_425932

编辑：Ameer Hamza 2020-4-14

在 MATLAB Online 中打开

Here is the simplified code

Vector = randi([0 99],10000,1);
range0to24 = sum(Vector >= 0 & Vector <= 24);
range25to49 = sum(Vector >= 25 & Vector <= 49);
range50to74 = sum(Vector >= 50 & Vector <= 74);
range75to99 = sum(Vector >= 75 & Vector <= 99);

You code is not working for several reasons. For example, in the line

if Vector (Vector >= 0 & Vector <= 24)

the Vector is a 10000x1 vector and you are comparing it with scalar. This does not make much sense in MATLAB. Also,

length(find(Vector>=75 & Vector<=99))

using length, and find together is redundant. You can simply sum the logical array.

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Ameer Hamza 2020-4-14

在 MATLAB Online 中打开

By not making sense, I meant that it is not doing what it might appear it does. This expression does have a meaning in MATLAB. If you give a vector as if condition and all the elements are non-zero, the MATLAB considers it as true. For example, try these two codes. First will print false and second will print true

if [1;0;1;1] % vector contains zero
    disp('true')
else
    disp('false')
end

and the seond code is

if [1;2;3;4] % no zero
    disp('true')
else
    disp('false')
end

Now, if consider your code, Vector (Vector >= 25 & Vector <= 49) have all non-zero elements so MATLAB consider it true and run

range25to49 = length(find(Vector>=25 & Vector<=49))

If you must use for loop then iterate on each element one by one.

Vector = randi([0 99],10000,1);
range0to24 = 0;
range25to49 = 0;
range50to74 = 0;
range75to99 = 0;
for i = 1:numel(Vector)
    if Vector (Vector(i) >= 0 && Vector(i) <= 24)
        range0to24 = range0to24 + 1;
    elseif Vector (Vector(i) >= 25 & Vector(i) <= 49)
        range25to49 = range25to49 + 1;
    elseif Vector (Vector(i) >= 50 && Vector(i) <= 74)
        range50to74 = range50to74 + 1;
    elseif Vector (Vector(i) >= 75 & Vector(i) <= 99)
        range75to99 = range75to99 + 1;
    end
end

SeungHyun Cha 2020-4-14

I fully understand Thank you a lot.

Thanks

Ameer Hamza 2020-4-14

I am glad to be of help.

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Conditional statement in random integers to classify

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