using logical functions to display arrays

Hello , I have an inquiry about a question that I am trying to solve:

I have tried solving it through making an M-file function named discount then making the following function:

function d=discount(x)
if x<10 
    d=0.95.*x;
elseif x>=10 & x<=30
    d=0.85.*x;
    
elseif x>30
    d=0.8.*x;
end

when I try calling the function in another file (after saving the previous function) and using P as an input:

P =[12 7.95 88 26.5 27.9 3.5 57 65.9 17.7 35.6 15 96.5 ]
discount(P)

I do not get any results!

I think the problem has to do with P consisting of numbers that undergo more than one condition but I still do not know the proper solution.

Answer 1

[David Hill]

P =[12 7.95 88 26.5 27.9 3.5 57 65.9 17.7 35.6 15 96.5 ];
discountedPrice=zeros(size(P));
discountedPrice(P<10)=P(P<10)*.95;
discountedPrice(P>=10&P<=30)=P(P>=10&P<=30)*.85;
discountedPrice(P>30)=P(P>30)*.8;

[Ibrahim Alsaif]

Thank you!

Answer 2

[the cyclist]

When x is a vector, then

if x < 10

is interpreted as "if all elements of x are less than 10". Your if statement is never entered.

You either need to use a for loop over x, or just use

x < 10

as a logical index.

[Ibrahim Alsaif]

Thank you!