1.5.4 Writing to a file🔗ℹ

With #:out-file, both plot procedures also write the plot to a file, in the format that the file’s extension names: ".png", ".pdf", ".svg" or ".eps", in upper or lower case. They still return the pict. Any other extension breaks their contract:

> (require racket/file)

> (define file (make-temporary-file "cv-~a.png"))

> (void (plot-cv cv #:out-file file))

> (call-with-input-file file (lambda (in) (read-bytes 4 in)))

#"\211PNG"

> (delete-file file)

> (plot-cv cv #:out-file "cv.jpg")

plot-cv: contract violation

expected: (or/c #f (and/c path-string?

has-image-extension?))

given: "cv.jpg"

in: the #:out-file argument of

(->*

((or/c glmnet-cv? formula-model?))

(#:height

exact-positive-integer?

#:out-file

(or/c

#f

(and/c

path-string?

has-image-extension?))

#:sign-lambda

(or/c -1 1)

#:title

(or/c #f string?)

#:width

exact-positive-integer?)

pict?)

contract from: <pkgs>/glmnet/plot.rkt

blaming: top-level

(assuming the contract is correct)

at: <pkgs>/glmnet/plot.rkt:80:3