[R] help with EXPASY HTML form submission in RCurl package

Duncan Temple Lang duncan at wald.ucdavis.edu
Fri Feb 12 21:54:08 CET 2010

Sunando Roy wrote:
> Hi,
> I am trying to submit a form to the EXPASY protscale server (
> http://www.expasy.ch/tools/protscale.html). I am using the RCurl package and
> the postForm function available in it. I have extracted the variables for
> the form from the HTML source page. According to the syntax of postForm, I
> just need to mention the url and assign values to the input mentioned in the
> HTML code.
> The code that I am using is:
> postForm("http://www.expasy.ch/tools/protscale.html",
>     "sequence" = "
>     scale = "Molecular weight",
>     window = "5",
>     weight_edges = "100",
>     weight_var = "linear",
>     norm = "no",
>     submit = "Submit"), .checkparams = TRUE)

I don't think that is what you actually submitted to R.
It is a syntax error as you end the cal to postForm) after "Submit"
and then have an extra  ", .checkparams = TRUE)" afterwards.

But, when you remove the ')' after  "Submit",
the problem you get is that .checkparams is not a parameter
of postForm(), but .checkParams is.  R is case-sensitive
so the problem is that .checkparams is being treated as a parameter
of your form.

So change the p to P in .checkparams, and it works.


> the constant error that I get is:
> Error in postForm("http://www.expasy.ch/tools/protscale.html", .params =
> list(sequence = "not",  :  STRING_ELT() can only be applied to a 'character
> vector', not a 'logical'
> Is there any other way to submit an HTML form in R ?
> Thanks for the help
> Regards
> Sunando
> 	[[alternative HTML version deleted]]
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

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