[datatable-help] subset data table in i with multiple criteria for multiple variables

[carlsutton]

Is there a way to subset a data table using "i" with multiple criteria using
multiple variables(columns)?  I have some test code shown below on what I
have tried.  And yes, I have read the documentation, taking the data camp
class (Multiple viewing, I'm  a slow learner) and have not seen anything
relevant.  Also checked for questions on this topic in this forum and did
not find an answer for my query.
Attempting to upload R file
dataTableExamples.R
<http://r.789695.n4.nabble.com/file/n4715347/dataTableExamples.R>  
Probably should have stayed in bed today the way things are going.

A cut and paste from RStudio
#  Data Table exercises
require(data.table)
a <- seq(2L,40L, by = 4L)
b <- seq(15L,105L,by = 10L)
c <- 1:10L
d <- rep(c(100L,150L),5L)
e <- 101:110L
dt <- data.table(a,b,c,d,e)
dt  
dta <- subset(dt, a < 35)
dtb <- subset(dta, b > 35)
dtb
dtb[, lapply(.SD,median), by = d]
#  Now attempt to subset the rows in i
vec <- c(a<35, b>35)
dtvec <- dt[vec, lapply(.SD, median, na.rm = TRUE), by = d]
dtvec

And console output
> #  Now attempt to subset the rows in i
> vec <- c(a<35, b>35)
> dtvec <- dt[vec, lapply(.SD, median, na.rm = TRUE), by = d]
Error in `[.data.table`(dt, vec, lapply(.SD, median, na.rm = TRUE), by = d)
: 
  Column 1 of result for group 2 is type 'double' but expecting type
'integer'. Column types must be consistent for each group.
> dtvec
     a  b  c   d   e
 1:  2 15  1 100 101
 2:  6 25  2 150 102
 3: 10 35  3 100 103
 4: 14 45  4 150 104
 5: 18 55  5 100 105
 6: 22 65  6 150 106
 7: 26 75  7 100 107
 8: 30 85  8 150 108
 9: 34 95  9 100 109
10: NA NA NA  NA  NA
11: NA NA NA  NA  NA
12: NA NA NA  NA  NA
13: NA NA NA  NA  NA
14: NA NA NA  NA  NA
15: NA NA NA  NA  NA
16: NA NA NA  NA  NA

The error message has me confused. 
 /Column 1 of result for group 2 is type/
What group 2?  I have only grouped on column "d".  Result 1 is ????  No idea
what "result 1" is referring to, is it the subset in "i", the median of col
a??  No clue.

I have only created integer variable for the data table, so why the
rejection " Column 1 of result for group 2 is type 'double' but expecting
type 'integer'. Column types must be consistent for each group."  What
double?  I have not created any double numbers.

Carl Sutton



-----
Carl Sutton
--
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