I can't comput the following commands

Question

Hong 2024-2-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2086103-i-can-t-comput-the-following-commands

编辑： Les Beckham 2024-2-23

if total>=90 && total<=100
    A1=sum(total>=90 && total<=100);
    frpintf('The number of A+ students is : %d\n',A1)
elseif total>=80 && total<90
    A=sum(total>=80 && total <90);
    frpintf('The number of A students is : %d\n',A2)
elseif total>= 70 && total<80
    B=sum(total >= 70 && total<80);
    fprintf('The number of B students is %d\n',B)
elseif total>=60 && total<70
    C=sum(total>=60 && total <70);
    fprintf('The number of C students is %d\n',C)
elseif total>=50 && total<60
    D=sum(total>=50 && total<60);
    fprintf('The number of D students is: %d\n',D)
elseif total>=40 && total<50
    E=sum(total>=40 && total<50);
    fprintf('The number of E students is: %d\n',E)
elseif total>=0 && total<40
    F=sum(total>=0 && total<40);
    fprintf('The number of F students is: %d\n',F)
end

Hi I tried to compute this commands to able get the number of student in each letter grade and I kept getting this error

"Operands to the logical AND (&&) and OR (||) operators must be convertible to logical scalar values. Use the ANY or ALL functions to reduce operands to logical scalar values.

Error in a3q5 (line 41)

elseif total>=80 && total<90"

Can someone please tell what's wrong with my commands, I try to fix but it does not seem really work

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Answer 1

John D'Errico 2024-2-23

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编辑：John D'Errico 2024-2-23

Sure you "can". It is just that MATLAB fails due to an error. :)

Anyway, you seem to think an if statement applies to each element of a vector, operating separately, doing something different for each element in that vector. It does not. An if statement is not a loop, though this is a common mistake made by new users.

If you are allowed to use it, I might recommend the function discretize to determine which interval each element of the total vector falls into. Then you could use arrayfun to count the number of students who fell in each grade bin.

Or, if that seems daunting, you could just use a simple loop. Loops are not a terrible thing. Just a little slow if you have too many of them.

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Answer 2

Walter Roberson 2024-2-23

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https://ww2.mathworks.cn/matlabcentral/answers/2086103-i-can-t-comput-the-following-commands#answer_1415473

编辑：Walter Roberson 2024-2-23

在 MATLAB Online 中打开

Remove all of the if statements. And convert the && to &

    A1=sum(total>=90 & total<=100);
    fprintf('The number of A+ students is : %d\n',A1)
    A=sum(total>=80 & total <90);
    fprint('The number of A students is : %d\n',A2)
    B=sum(total >= 70 & total<80);
    fprintf('The number of B students is %d\n',B)
    C=sum(total>=60 & total <70);
    fprintf('The number of C students is %d\n',C)
    D=sum(total>=50 & total<60);
    fprintf('The number of D students is: %d\n',D)
    E=sum(total>=40 & total<50);
    fprintf('The number of E students is: %d\n',E)
    F=sum(total>=0 & total<40);
    fprintf('The number of F students is: %d\n',F)