adding as integers instead of list elements in R

Question

I am getting

> total = 0
> for (qty in a[5]){
+ total = total + as.numeric(unlist(qty))
+ print(total)
+ }
 [1] 400 400 400 400 400 400 400 400 400 400

what i really want is :

> total = 0
> for (qty in a[5]){
+ total = total + as.numeric(unlist(qty))
+ print(total)
+ }
 [1] 400 800 1200 1600 2000 2400 2800 3200 3600 4000

refine: a little bit more to a more specific scenario,

price buy_sell  qty
100        B  100
100        B  200
90        S  300
100        S  400

I want to make a forth column

price buy_sell  qty net
100        B  100   10000
100        B  200   30000
90        S  300    3000
100        S  400   -37000

What is `a[5]`? (Best would be to post the result of `dput(a[5])`) — David Robinson, Mar 01 '13 at 21:31
a5 is a list of integers: > a[5] qty 1 412 2 400 3 432 4 400 5 453 6 400 7 392 8 400 9 302 10 400 — danielho, Mar 01 '13 at 21:39
hi danielho, can you please copy the `dput` statement @DavidRobinson mentioned and paste the output into your question above — Ricardo Saporta, Mar 01 '13 at 21:42
> dput (a[5]) structure(list(qty = c(100L, 200L, 300L, 400L, 500L, 600L, 700L, 800L, 900L, 1000L)), .Names = "qty", class = "data.frame", row.names = c(NA, -10L)) — danielho, Mar 01 '13 at 21:49
@danielho, sorry, but your edit makes no sense relative to your original question. — Ricardo Saporta, Mar 01 '13 at 21:56
yes you are right Ricardo, I asked the wrong question as I was trying to split the problem up. — danielho, Mar 01 '13 at 22:17
You're more than welcomed to add a new question. Why not put your question back to how it was and ask a new question — Ricardo Saporta, Mar 02 '13 at 01:26

score 2 · Answer 1 · answered Mar 01 '13 at 21:35

2

Note that if a is a list, you want to use double brackets. Otherwise you are getting back a list of size one, where the first element has the values you are looking for

Try:

 total <- cumsum(a[[5]])

a <- list()
a[[5]] <- rep(400, 10)

cumsum(a[[5]])
#  [1]  400  800 1200 1600 2000 2400 2800 3200 3600 4000

Compare:

 a[5]
 a[[5]]
 a[5][[1]]

answered Mar 01 '13 at 21:35

Ricardo Saporta

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You might be able to add more characters by explaining the difference between `[` and `[[` for lists, which is probably why the OP's loop isn't working the way they expect. :) – joran Mar 01 '13 at 21:37
@Joran hahaha, i was typing just that as you wrote your comment ;) – Ricardo Saporta Mar 01 '13 at 21:39
@Joran, however, it could be that `a` is *not* a list, or `as.numeric(a[5])` would throw an error – Ricardo Saporta Mar 01 '13 at 21:41
is there anyway to look at the source of cumsum? i want to modify it a little – danielho Mar 01 '13 at 21:50
Absolutely! Take a look at http://stackoverflow.com/questions/14035506/how-to-see-the-source-code-of-r-internal-or-primitive-function/14035586#14035586 – Ricardo Saporta Mar 01 '13 at 21:52

adding as integers instead of list elements in R

1 Answers1