[datatable-help] Apparent loss of decimals when reading a numeric column with fread() !

Bacou, Melanie mel at mbacou.com
Tue Aug 4 15:06:06 CEST 2015


Right, thanks Frank. Sorry, I think fatigue is piling up here!
--Mel.

On 8/4/2015 9:02 AM, Frank Erickson wrote:
> .I was never an index by group. You'd have to make that more manually, 
> like 1:.N
>
> On Tue, Aug 4, 2015 at 8:54 AM, Bacou, Melanie <mel at mbacou.com 
> <mailto:mel at mbacou.com>> wrote:
>
>     Starting to wonder if something else is going on with my R
>     install. Using the same CSV file, I'm not getting what I expect
>     with `.I` (I would expect an index by group).
>
>     ```
>     pcn08 <- fread("./data/PovCalServlet_15.08.03.csv")
>
>     # and then grouping by 2 fields
>     pcn08[, test := .I, by=list(country, povLine)]
>
>     pcn08$test
>     # [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20
>     21 22 23 24 25 26 27
>     # [28] 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
>     48 49 50 51 52 53 54
>     # [55] 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74
>     75 76 77 78 79 80 81
>     # [82] 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98
>
>     # but there are 86 groups
>     dim(pcn08[, .N, by=list(country, povLine)])
>     # [1] 86  3
>
>     ```
>
>
>     On 8/4/2015 8:06 AM, Bacou, Melanie wrote:
>
>         In case that happens to others. Seems related to R global
>         `digits` options, maybe something changed in R.3.2.1.
>         --Mel.
>
>         ```
>         options(digits=3)
>         1000-0.5
>         # [1] 1000
>         options(digits=5)
>         1000-0.5
>
>         # [1] 999.5
>
>         ```
>
>         On 8/4/2015 7:54 AM, Bacou, Melanie wrote:
>
>             Hi,
>             Thx, I see I have another problem, not related to
>             data.table (sorry). R seems to truncate numbers in the
>             console. Not sure what's going on.
>
>             --Mel.
>
>             ```{r}
>             > 1-0.5
>             [1] 0.5
>             > 2008-0.05
>             [1] 2008
>             > 45-0.5
>             [1] 44.5
>             > 100-0.5
>             [1] 99.5
>             > 1000-0.5
>             [1] 1000
>             > 10000-0.5
>             [1] 10000
>             ```
>
>             On 8/4/2015 7:16 AM, nachti wrote:
>
>                 Hi,
>                 copying your code, everything works as expected for me.
>                 Maybe you just referenced to a wrong object (pcn08)?
>
>                 ```
>
>                     library(data.table)
>
>                 data.table 1.9.4  For help type: ?data.table
>                 *** NB: by=.EACHI is now explicit. See README to
>                 restore previous behaviour.
>
>                     pcn <- fread("PovCalServlet_15.08.03.csv")
>
>                 sapply(pcn, class)
>                 pcn <- fread("PovCalServlet_15.08.03.csv")
>
>                     sapply(pcn, class)
>
>                      country     povLine        mean         hcr gap sev
>                 "character"   "numeric"   "numeric"   "numeric"
>                  "numeric" "numeric"
>                        watts        popM     yearNum
>                    "numeric"   "numeric"   "numeric"
>
>                     pcn08$yearNum
>
>                 Error: object 'pcn08' not found
>
>                     pcn$yearNum
>
>                   [1] 2008.50 2011.50 2009.25 2009.00 2006.00 2007.50
>                 2007.00 2008.00 2011.00
>                 [10] 2004.00 2005.50 2011.00 2008.00 2010.50 2005.00
>                 2003.00 2005.50 2008.00
>                 [19] 2007.00 2012.00 2002.00 2005.40 2010.00 2007.00
>                 2010.00 2010.23 2010.00
>                 [28] 2008.00 2008.00 2012.00 2006.00 2008.64 2009.50
>                 2011.00 2009.83 2010.83
>                 [37] 2010.00 2011.00 2006.50 2011.00 2010.67 2009.00
>                 2009.50 2011.80 2011.00
>                 [46] 2008.00 2012.50 2009.30 2010.00 2008.50 2011.50
>                 2009.25 2009.00 2006.00
>                 [55] 2007.50 2007.00 2008.00 2011.00 2004.00 2005.50
>                 2011.00 2008.00 2010.50
>                 [64] 2005.00 2003.00 2005.50 2008.00 2007.00 2012.00
>                 2002.00 2005.40 2010.00
>                 [73] 2007.00 2010.00 2010.23 2010.00 2008.00 2008.00
>                 2012.00 2006.00 2008.64
>                 [82] 2009.50 2011.00 2009.83 2010.83 2010.00 2011.00
>                 2006.50 2011.00 2010.67
>                 [91] 2009.00 2009.50 2011.80 2011.00 2008.00 2012.50
>                 2009.30 2010.00
>
>                     sessionInfo()
>
>                 R version 3.2.1 (2015-06-18)
>                 Platform: x86_64-suse-linux-gnu (64-bit)
>                 Running under: openSUSE 13.1 (Bottle) (x86_64)
>
>                 locale:
>                   [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
>                   [3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
>                   [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
>                   [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
>                   [9] LC_ADDRESS=C               LC_TELEPHONE=C
>                 [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
>
>                 attached base packages:
>                 [1] stats     graphics  grDevices utils  datasets 
>                 methods base
>
>                 other attached packages:
>                 [1] data.table_1.9.4
>
>                 loaded via a namespace (and not attached):
>                 [1] compiler_3.2.1 magrittr_1.5   plyr_1.8.3  tools_3.2.1
>                 reshape2_1.4.1
>                 [6] Rcpp_0.11.6    stringi_0.5-5  stringr_1.0.0
>                 chron_2.3-4
>                 ```
>
>                 ~g
>
>
>
>                 -- 
>                 View this message in context:
>                 http://r.789695.n4.nabble.com/Apparent-loss-of-decimals-when-reading-a-numeric-column-with-fread-tp4710722p4710727.html
>                 Sent from the datatable-help mailing list archive at
>                 Nabble.com.
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