Calculating values using for loops

I want to perform the following calculations using for loops. The user enters the inputs the value and the index is set. I want to calculate every index three times, since my first condition in the for loop is if idx(x) <= a(:), variable a=[2,3,4]. So the first time that it calculates the first set would be

idx(x)<=2 using B(1) C(1) and then idx(x)<=3 using B(2) C(2) and lastly idx(x)<=4 using B(3) C(3). How can i make it work using for loops?

I get an error that states 'Unable to perform assignment because the indices on the left side are not compatible with the size of the right side.'

n=input('From zero, until what number do you want to calculate.Enter value:');
idx=0:0.1:n ;
a=[2,3,4];
B=[4,6,8];
C=[2,6,7];
v=[];
for x=1:length(idx)
    if idx(x) <= a(:)
        v(x)=-C.*idx(x)+B.*2;
    else
        v(x)=-C.*idx(x)+B.*2+(B./2).*2
    end
end

[Stephen23]

Earlier question:

https://www.mathworks.com/matlabcentral/answers/509479-calculations-using-for-loops

Answer 1

[Ameer Hamza]

The error message is pretty self-explanatory. The dimension of -C.*idx(x)+B.*2 is 1x3, whereas you are trying to assign it to a single element of a numeric array. Without any context, the following are the few possible solutions to get rid of this error

for x=1:length(idx)
    if idx(x) <= a(:)
        v(x,:)=-C.*idx(x)+B.*2;
    else
        v(x,:)=-C.*idx(x)+B.*2+(B./2).*2;
    end
end

This will create the vector v with the dimension of 101x3.

The other solution is to create a cell array

for x=1:length(idx)
    if idx(x) <= a(:)
        v{x}=-C.*idx(x)+B.*2;
    else
        v{x}=-C.*idx(x)+B.*2+(B./2).*2;
    end
end