sunnypy sunnypy - 1 month ago 17
R Question

Very basic R - I want to write a function that generates two vectors in R^2

I'm new in R. And I want to write a function that generates two vectors in R^2
And this function does the following:
1.It takes these two R^2 vectors as the two arguments.
2.It calculates the distance and angle between the two vectors.
3.It projects the fi rst vector onto the second vector.
4.It visualize the projection result.

I tried the codes:

x <- function(x)
y <- function(y)
distance <- (sqrt(sum(x*x))*sqrt(sum(y*y)))
theta <- -acos(sum(x*x)/distance)
proj <- (x%*%y)/norm(y)%*%y
if (length(x)==2 & length (y) ==2)
{ print(distance) &
print(theta) &
print(proj)
}else {
print("Not R^2 vectors")
}


And I got the error message:

> x <- function(x)
+ y <- function(y)
+ distance <- (sqrt(sum(x*x))*sqrt(sum(y*y)))
> theta <- -acos(sum(x*x)/distance)
**Error in x * x : non-numeric argument to binary operator**
> proj <- (x%*%y)/norm(y)%*%y
**Error: object 'y' not found**
> if (length(x)==2 & length (y) ==2)
+ { print(distance) &
+ print(theta) &
+ print(proj)
+
+ }else {
+ print("Not R^2 vectors")
+ }
**Error: object 'y' not found**


I've tried to fix my code for hours and it still didn't work. Also, I don't know which command to use to visualize the projection result. Could anyone please help me with this? I'd really appreciate that!

Answer

Are you planning to call this as a single function? Maybe you'd be better served with a single function with multiple input parameters, rather than multiple functions:

func <- function(x, y) {
    distance <- (sqrt(sum(x*x))*sqrt(sum(y*y)))
    theta <- -acos(sum(x*x)/distance)
    proj <- (x%*%y)/norm(y)%*%y
    if (length(x)==2 & length (y) ==2)
    { print(distance) &
            print(theta) &
            print(proj)      
    }else {
        print("Not R^2 vectors")
    }  
}

So you'd call it with something like:

output <- func( x, y )

Or, perhaps more clearly:

output <- func( x = x, y = y )

Note: I'm not addressing anything within your function, only the way it's created and called. The function itself doesn't make a lot of sense to me, so I won't try to edit that.

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