You REALLY NEED to read the "Introduction to R" document discussion of
indexing.
tab is a variable. It is apparently a data.frame. tab[[mvar]] is an expression
that retrieves part of the data in the tab data.frame. The data it returns is a
vector, not a data.frame.
The "[[" operator extracts
If 'tab' is a data.frame then new.tab <- tab[[mvar]] is a column from that
data.frame, not a data.frame with one column. new.tab <- tab[ , mvar,
drop=FALSE ] will give you a data.frame that you can add to with either of
nvar <- "newName"
new.tab[ , nvar] <- newColumn
new.tab[[nvar]] <-
Yes, you can use a name stored in a variable to create a new column in a
data frame (guessing that's what you want). Here's an example:
> df <- data.frame(a=1:5)
> df[['b']] <- 2:6
> df
a b
1 1 2
2 2 3
3 3 4
4 4 5
5 5 6
> mvar <- 'c'
> df[[mvar]] <- 0:4
> df
a b c
1 1 2 0
2 2 3 1
3 3 4 2
4 4 5
See
Example 5. Insert Variables
on the sqldf home page.
https://github.com/ggrothendieck/sqldf
On Wed, Feb 3, 2016 at 2:16 PM, Amoy Yang via R-help
wrote:
> First, MVAR<-c("population) should be the same as "population'". Correct?
> You use tab[[MVAR]] to refer to "population" where doub
> On Feb 3, 2016, at 11:57 AM, Amoy Yang via R-help
> wrote:
>
> Right! the following works to r but not sqldf.
> MVAR <- "population"
> tab[[ MVAR ]]
> sqldf("select tab[[MVAR]] from tab")
If ypu need a string to pass to sqldf, then use the `paste` function to build a
single string:
sqldf(
Right! the following works to r but not sqldf.
MVAR <- "population"
tab[[ MVAR ]]
sqldf("select tab[[MVAR]] from tab")
On Wednesday, February 3, 2016 1:18 PM, Amoy Yang via R-help
wrote:
First, MVAR<-c("population) should be the same as "population'". Correct?
You use tab[[MVAR]] to re
Repeat many times: R does not work the same way as SAS, do not expect it
to
If I needed to construct an SQL statement in which the name of a field is
provided by the value of another variable, I would consider this:
key <- 'pop'
sql.stmt <- paste("select grade,
count(*) as cnt,
min(",key,") a
First, MVAR<-c("population) should be the same as "population'". Correct?
You use tab[[MVAR]] to refer to "population" where double [[...]] removes
double quotes "...", which seemingly work for r-code although it is tedious in
comparison direct application in SAS %let MVAR=population. But it does
Are you perhaps needing to (re-)read the discussion on indexing in the
"Introduction to R" document that comes with the software? (That is a common
deficiency...)
It looks to me like you want something like
MVAR <- "population"
tab[[ MVAR ]]
--
Sent from my phone. Please excuse my brevity.
O
I am not sure what you want, but:
1) If you have not already done so, go through an R tutorial or two.
For some suggestions:
https://www.rstudio.com/resources/training/online-learning/#R
R is quite different than SAS.
2) If I misunderstand, perhaps
?within
is what you are looking for.
Cheer
Hello,
You can't use tab$MVAR but you can use tab[[MVAR]] if you do MVAR <-
"population" (no need for c()).
Hope this helps,
Rui Barradas
Citando Amoy Yang via R-help :
> population is the field-name in data-file (say, tab).
> MVAR<-population takes data (in the column of population) rat
On 03/02/2016 1:23 PM, Amoy Yang wrote:
population is the field-name in data-file (say, tab). MVAR<-population takes
data (in the column of population) rather than field-name as done in SAS: %let
MVAR=population;
In the following r-program, for instance, I cannot use ... tab$MVAR...or simply M
population is the field-name in data-file (say, tab). MVAR<-population takes
data (in the column of population) rather than field-name as done in SAS: %let
MVAR=population;
In the following r-program, for instance, I cannot use ... tab$MVAR...or simply
MVAR itself since MVAR is defined as "popu
On 03/02/2016 12:41 PM, Amoy Yang via R-help wrote:
There is a %LET statement in SAS: %let MVAR=population; Thus, MVAR can be
used through entire program.
In R, I tried MAVR<-c("population"). The problem is that MAVR comes with double quote
"" that I don't need. But MVAR<-c(population) di
Don't know what `population` is, but a simple assignment
MVAR <- population
may provide what you need. Note, no c(). For example,
> foo <- rnorm
> foo(3)
[1] -0.08093862 -0.87827617 1.52826914
/Henrik
On Wed, Feb 3, 2016 at 9:41 AM, Amoy Yang via R-help
wrote:
> There is a %LET statement
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