Error when defining variable with if statement and add to table

Hello! I want to define the variable 'm' with an if statement with 3 conditions and add this defined variable to a table for further calculations. But using this code gives me an error.

a=[1,2];
b=[2,6,10];
l=[1:20:100];

[a,b,l]=ndgrid(a,b,l);

a=a(:);
b=b(:);
l=l(:);
disp=([a,b,l])

if (b==2)
    m = 100
elseif (b==6)
    m = 1000
elseif (b==10)
    m = 10000
end

disp([a,b,l,m])

Error using horzcat

Dimensions of arrays being concatenated are not consistent.

Error in test (line 20)

disp([a,b,l,m])

Does someone know what I´m doing wrong?

Answer 1

[Fangjun Jiang]

the size of a, b and l is 30x1 but the size of m is 1x1

[Fangjun Jiang]

I guess you want

m=b;
m(b==2)=100
m(b==6)=1000
m(b==10)=10000

then you can do

disp([a,b,l,m])

Answer 2

[KALYAN ACHARJYA]

First Issue:

a=[1,2];
b=[2,6,10];
l=[1:20:100];
[a,b,l]=ndgrid(a,b,l);
a=a(:);
b=b(:);
l=l(:);
disp=([a,b,l])
if (b==2)
    m = 100
elseif (b==6)
    m = 1000
elseif (b==10)
    m = 10000
end
disp([a,b,l,m])

If you run the code, you will get the error, as m is undefined, as neither b==2,b==6 or b==10, b value from the code is vector 30x1, not scalar single value. These if condition are not satisfied in any three cases, therefore m value is not assigned, so its reflects the error m is undefined.

Second Case:

If you manage to run the if condition anyhow, then m value assigned as one scalar value.

Due to different sizes of a,b,l,m, it cannot concanated. Where a,b,l are 30x1, whereas m will a scalar value.

Hope it helps!

Answer 3

[Patrick Maier]

Ok got it. How can I change the if statement that m will also be a 30x1 vector with this conditions?

Like:

b m

2 100

6 1000

10 10000

..

[Fangjun Jiang]

You could use the code in my answer, or

m=b;
for k=1:numel(m)
    if b(k)==2
        m(k) = 100;
    elseif b(k)==6
        m(k) = 1000;
    elseif b(k)==10
        m(k) = 10000;
    end
end

Answer 4

[Patrick Maier]

Thank you so much!!