[datatable-help] Avoiding print when using := ?

[Steve Lianoglou]

Hi,

On Fri, Sep 14, 2012 at 1:56 AM, Allan Engelhardt (CYBAEA)
<allane at cybaea.com> wrote:
> On 13/09/12 23:42, Steve Lianoglou wrote:
>>
>> Perhaps the `nrows` param in print.data.table should be user
>> configurable by some `option`, maybe something like:
>>
>> print.data.table <- function(x,
>> nrows=getOption('datatable.print.nrows', 100), ...) { ... }
>>
>> Then you could `options(datatable.print.nrows=20)` if 100 is too high ...
>>
>> Maybe?
>>
>> -steve
>
>
> I really like this suggestion. You could perhaps even set it to 0
> temporarily while you were doing lots of := work. Do you want to raise a
> feature request Steve?

I just committed code to SVN to support this. In short there are two
new `options` one can set to customize the amount of a data.table
summariazed to the console (these can always be sidestepped by calling
`print(dt)` directly).

The options are:

* datatable.print.nrows : When the data.table has more than this
number (defaults to 100) the `---` summary stuff is triggered. If this
is set to 0, no data.table will be printed to the console unless you
call `print(your.data.table, ...)`

* datatable.print.topn : When a summary is triggered during printing,
this number show the top and bottom `topn` rows (defaults to 10)

FAQs 2.11 and 2.22 to show you how you might use it, but in short:

R> library(data.table)
R> dt = data.table(a=letters[1:10], b=rnorm(10))
R> options(datatable.print.nrows=8)
R> dt
    a          b
 1: a -1.1423662
 2: b  0.2878413
---
 9: i -0.1247109
10: j -0.6932983

R> dt[, something := rnorm(10)]
    a          b    something
 1: a -1.1423662  0.700697859
 2: b  0.2878413 -0.007995077
---
 9: i -0.1247109  0.060807862
10: j -0.6932983 -0.796266433

R> options(datatable.print.nrows=0)
R> dt[, another := runif(10)]
R> print(dt, 100)
    a          b    something   another
 1: a -1.1423662  0.700697859 0.3831220
 2: b  0.2878413 -0.007995077 0.3894803
 3: c -0.9657560 -0.511566173 0.1208057
 4: d -0.1065197  0.685830341 0.2878074
 5: e -0.7630674 -0.161960447 0.3378524
 6: f -1.1561141  0.464995932 0.2487832
 7: g  0.2408447 -0.175998144 0.8600236
 8: h -0.4386328  1.002378381 0.7682450
 9: i -0.1247109  0.060807862 0.1635926
10: j -0.6932983 -0.796266433 0.4739380

The caveat is that I didn't check in with Matthew to see if he's OK
with this, so unless he objects ... there it is. It is in SVN now (at
r-forge), and you can grab it from there and install. If you aren't
setup to do that, you will have to wait for 1.8.3 to release.

The other thing is that this really doesn't address the `:=` printing
behavior specifically, so not sure how helpful this is in the long run
unless you don't mind calling `print` to view things explicitly.

HTH,
-steve

-- 
Steve Lianoglou
Graduate Student: Computational Systems Biology
 | Memorial Sloan-Kettering Cancer Center
 | Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact