print table in R using names from vector

Question

I am trying to create a number of table objects that I can insert into an html page unsing Knit and would like to be able to loop through a vector of names to print the corresponding table.

for example:

TabA = as.table(cbind(c("A","B","C"),c(1,2,3)))
TabB = as.table(cbind(c("D","E","F"),c(1,2,3)))

nams = c("TabA","TabB")

Then in the html using R markdown

Example Table: `r nams[4] `

```{r}
knitr::kable(t(nams[4]),format = "markdown")
```

I know how to assign names on the fly, but not sure how to use the vector as a pointer to the object.

You can use `get`, as in, say, `tab = get(nams[i])` or `print(get(nams[i]))`. — eipi10, Mar 13 '15 at 20:02
Why not `tabs = list(TabA, TabB); lapply(tabs, print)` ? It's a much better use of R — Señor O, Mar 13 '15 at 20:19
I'm unclear what you're really trying to do but as a side note `as.table(cbind(...))` might not be the best way to create your data or even what you would expect, since the numeric vector `c(1,2,3)` is converted to character. There was a similar issue [in this question](https://stackoverflow.com/questions/28992362/dplyr-join-define-na-values/28995196#28995196) recently. — talat, Mar 13 '15 at 21:02

Dominic Comtois · Answer 1 · 2015-03-16T15:02:19.537

Not sure where the html file comes in, but for the names issue, it might be wiser to just use a list (and thus avoid any evaluating of strings):

my.tables <- list(TabA=as.table(cbind(c("A","B","C"),c(1,2,3))),
                  TabB=as.table(cbind(c("D","E","F"),c(1,2,3))))

for(tab.name in names(my.tables))
  print(my.tables[[tab.name]])

# Or if you don't like loops
invisible(lapply(my.tables, print))

#   A B
# A A 1
# B B 2
# C C 3
#   A B
# A D 1
# B E 2
# C F 3

score 1 · Accepted Answer · answered Mar 13 '15 at 20:16

1

You can use get, as in:

tab = get(nams[i]) or print(get(nams[i])).

get("string") returns the object with name equal to "string"

answered Mar 13 '15 at 20:16

eipi10

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score 0 · Answer 3 · answered Mar 13 '15 at 20:08

eval(parse(text="some clever text here")) will take a string and evaluate it as an expression. You might try something like the following

for(i in names) {
    print(eval(parse(text = i)))
}

parse: https://stat.ethz.ch/R-manual/R-devel/library/base/html/eval.html

eval: https://stat.ethz.ch/R-manual/R-devel/library/base/html/parse.html

score 0 · Answer 4 · answered Mar 13 '15 at 20:21

0

If you just want the side-effect of printing then this succeeds with no loop or clunky eval(parse(.)). The mget function provides implicit looping:

invisible(sapply( mget(nams), print))
  A B
A A 1
B B 2
C C 3
  A B
A D 1
B E 2
C F 3

The invisible is used to suppress the extra values that print returns to sapply. You could also drop the invisible wrapper if you assigned the result to a temp variable.

answered Mar 13 '15 at 20:21

IRTFM

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That would work, but I have to place text in between the tables. – user44796 Mar 13 '15 at 20:56
If you don't describe the problem completely there's a low probability that the answers will be totally satisfactory. – IRTFM Mar 13 '15 at 21:03
I have hopefully clarified the question. You are right that I was unclear. – user44796 Mar 16 '15 at 14:53

score -1 · Answer 5 · answered Mar 13 '15 at 20:08

-1

You should use eval and as.name

TabA = as.table(cbind(c("A","B","C"),c(1,2,3))) 
TabB = as.table(cbind(c("D","E","F"),c(1,2,3)))

nams = c("TabA","TabB")

for (i in 1:length(nams)) {
    print(eval(as.name(nams[i])))
}

answered Mar 13 '15 at 20:08

Philippe Chavanne

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print table in R using names from vector

5 Answers5