Subtracting in matrix, column to column (Basic MatLab)?

Given a 45×48 matrix, type a single command that subtracts column 36 from column 44

i answered this but it pops up as Error: Invalid use of operator. Is there something wrong or should it be in different type of form.

(:,36)-(:,44)

Answer 1

[Star Strider]

Your idea is essentially correct. I have no idea what the question wants.

Perhaps providing a matrix and a reference to it will work:

A = rand(45,48);
col_dif = A(:,36)-A(:,44)

[John wick]

This is the question "Given a 45×48 matrix, type a single command that subtracts column 36 from column 44"

It's told to be in 1 command but when i try it was an error

col_dif = A(:,36)-A(:,44)

Is this how we need to write? We do need to have the = and A right?

Thank you very much~

[Star Strider]

‘... subtracts column 36 from column 44 ...’

I missed the obvious!

Try this instead:

col_dif = A(:,44)-A(:,36)

[John wick]

Why did you swap the 44 and 36?

[Star Strider]

Because the instruction is that the operation ‘... subtracts column 36 from column 44 ...’, and

col_dif = A(:,44)-A(:,36)

is the correct operation to subtract column 36 from column 44.

The reference to column 44 must come first in the order of operations, then the subtraction operation and then the value to be subtracted from column 44, here column 36. (There are other ways to code that subtraction and still get the correct result, however this is the most efficient.)

[John wick]

Ohhh Thank you very much for helping and explaining it. Love ya!

[Star Strider]

As always, my pleasure!

Answer 2

[Image Analyst]

You need to put the matrix name in there, and a result variables, like

result = m(:,44) - .....................

etc.

[John wick]

Because the given question is "Given a 45×48 matrix, type a single command that subtracts column 36 from column 44" and nothing else. it kind of make me confuse of what exactly I need to write. Thank youu

[Image Analyst]

Well you can't just have indexes within parentheses like (:,44), because how could MATLAB possibly know which matrix you're referring to.

[John wick]

I guess i just got the idea on how it works but not really master it. Thank you for helping me out!