CODEWITHSUNDEEP
rgraphics
isomorphismes
isomorphismes

Reputation: 8403

Cannot coerce type 'closure' to vector of type 'double' (polygon)

plot( dnorm , col='white')
polygon( dnorm, col='grey' )

returns the above error message, not on plot, but on polygon.

body(polygon) %>% grep(pattern='numeric') finds only one occurrence on line 4, which doesn't seem to have anything to do with this error. So I'm at a loss as to where to look for the source of the problem.

Upvotes: 1

Views: 3595

Answers (3)

isomorphismes
isomorphismes

Reputation: 8403

You need to polygon( dnorm(-3:3) ) or whatever the xlim limits are. polygon lacks a method for treating functions (although plot has one).

Upvotes: 0

BrodieG
BrodieG

Reputation: 52637

plot has a function method, whereas polygon does not. From ?plot:

x: the coordinates of points in the plot. Alternatively, a single plotting structure, function or any R object with a plot method can be provided.

Additionally, from ?plot.function, the S3 method to plot functions:

## S3 method for class 'function'
plot(x, y = 0, to = 1, from = y, xlim = NULL, ylab = NULL, ...)

This explains why you get a plot with values from 0 to 1 with plot when you pass dnorm as an argument.

Note functions like dnorm are also known as closures. This explains why you get that error with polygon. Since polygon does not accept functions as an argument, it tries to convert dnorm, a closure, to a vector, but that isn't a valid conversion.

The error in polygon is actually happening in the as.double call within xy.coord:

> polygon(dnorm)
Error in as.double(y) : 
  cannot coerce type 'closure' to vector of type 'double'
> traceback()
2: xy.coords(x, y)
1: polygon(dnorm)

Note as.double doesn't register in the trace stack because it is a primitive. By looking at the source of xy.coords, you can see where the error is happening. To semi-confirm:

> as.double(dnorm)
Error in as.double(dnorm) : 
  cannot coerce type 'closure' to vector of type 'double'

dnorm(-3:3) actually produces a numeric vector, which is why that works with polygon.

Upvotes: 3

vpipkt
vpipkt

Reputation: 1707

The call to plot will resolve to a variety of default methods for different types of objects. See methods(plot) for a list in your environment. For dnorm it is plot.function, which takes the function as an argument and provides a set of inputs into the function. Incidentally this will also work with rnorm because plot.function provides a default argument of n=101.

A more common alias for plot.function is curve.

curve(dnorm, col="grey")

The polygon has no such analogous method for various types of objects.

Upvotes: 0

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