[R] Evaluation failure of IAPWS95 functions in a rowwise manner (tidyverse style)

[Shawn Way]

The printed output is an issue (I've emailed the maintainer about it) however, I think I figured it out.

It seems that the function is not vectorized, making me need to do the following: 

mutate(SG=map2(T,p,function(x,y) DTp(x,y))

This was able to get the correct results.  Like usual, the error was between the head and the keyboard.

Thanks!

Shawn Way

-----Original Message-----
From: Ista Zahn <istazahn using gmail.com> 
Sent: Wednesday, May 30, 2018 2:28 PM
To: Shawn Way <SWay using meco.com>
Cc: r-help using r-project.org
Subject: Re: [R] Evaluation failure of IAPWS95 functions in a rowwise manner (tidyverse style)

Hi Shawn,

I don't think it has anything to do with the tidyverse. If you keep simplifying your example you'll get all the way down to

> DTp(T=c(279,294),p=c(0.46,0.46))
[1] 1000.12283

--Ista

On Wed, May 30, 2018 at 2:14 PM, Shawn Way <SWay using meco.com> wrote:
> I'm trying to use the IAPWS95 package with the tidyverse packages.  For some reason, the function is not outputting the correct rho.
>
> A minimal example with results is below.  I've also included the definition of the DTp function from the IAPWS95 library.
> ====================================
> library(IAPWS95)
> library(tidyverse)
>
> initial <- data.frame(T=c(279,294),p=c(0.46,0.46))
> initial2 <- initial %>%
>     mutate(rho=DTp(T,p))
>
>> DTp
> function (T, p)
> {
>     y <- 0
>     icode <- 0
>     res <- .Fortran("DTp", as.double(T), as.double(p), as.double(y),
>         as.integer(icode))
>     options(digits = 9)
>     if (res[[4]] != 0) {
>         error <- as.character(errorCodes[which(errorCodes[, 1] ==
>             res[[4]]), 2])
>         print(error)
>     }
>     print(res[[3]])
> }
> <bytecode: 0x0000000006f520e0>
> <environment: namespace:IAPWS95>
>
> Results:
>
>> initial2
>     T    p        rho
> 1 279 0.46 1000.12283
> 2 294 0.46 1000.12283
>
>
> What the results should be:
>
>> initial2
>     T    p        rho
> 1 279 0.46 1000.12283
> 2 294 0.46 998.19167
>
> I think something is evaluating incorrectly, but I don't know enough about NSE vs SE to figure this out.
>
> Any thoughts to what could be the reason why the second row has the same rho as the first?  When I run the function DTp individually, I get the right results.
>
>
> Shawn Way
>
>
>
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