[R] saveRDS() and readRDS() Why? [solved, pretty much anyway)

[p_connolly]

On 2018-11-12 22:49, peter dalgaard wrote:
> Er, where, what, how? I can't reproduce that, at least not on 3.5.1 on 
> MacOS:
> 
>> x <- airquality
>> saveRDS(x, file = "x.rds")
>> x <- NULL
>> x <- readRDS(file = "x.rds")
>> x
>     Ozone Solar.R Wind Temp Month Day
> 1      41     190  7.4   67     5   1
> 2      36     118  8.0   72     5   2
> 3      12     149 12.6   74     5   3
> ...
> 
> Looks fine to me.
> 

It seems to work fine using the same installation to read as used for 
the save.
But it's a different story if the save was done on a Windows 
installation and read on a Linux installation.

## On Windows 3.4.2
> x <- airquality
> saveRDS(x, file = "x.rds")
> saveRDS(x, file = "y.rds")

Files x.rds and y.rds are identical in size but utterly different in 
content.

## On Linux 3.5.1

> x <- readRDS(file =  "x.rds")
Error in readRDS(file = "x.rds") : error reading from connection
> x <- readRDS(file =  "y.rds")
> head(x)
   Ozone Solar.R Wind Temp Month Day
1    41     190  7.4   67     5   1
2    36     118  8.0   72     5   2
3    12     149 12.6   74     5   3
4    18     313 11.5   62     5   4
5    NA      NA 14.3   56     5   5
6    28      NA 14.9   66     5   6

It might just be the age of the Windows installation.  I don't have much 
use for Windows, so I haven't had much inclination to install a newer 
version.

YMMV



> ?
> -pd
> 
> 
>> On 12 Nov 2018, at 08:28 , Patrick Connolly 
>> <p_connolly using slingshot.co.nz> wrote:
>> 
>> The solution was very simple.  Don't use the same name for the rds
>> file  as used for the R object, viz a vie:
>> 
>> saveRDS(x, file = "x.rds")
>> and
>> x <- readRDS(file = "x.rds")
>> 
>> will not work; however
>> 
>> saveRDS(x, file = "y.rds")
>> and
>> x <- readRDS(file = "y.rds")
>> will work.
>> 
>> An undocumented feature?
>> 
>> Thanks to all who contributed.
> 
> --
> Peter Dalgaard, Professor,
> Center for Statistics, Copenhagen Business School
> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> Phone: (+45)38153501
> Office: A 4.23
> Email: pd.mes using cbs.dk  Priv: PDalgd using gmail.com