ldply fails if .fun gives NA as a column name

[scottkosty]

ldply has trouble when .fun passes a return with NA as a column name. The following shows a fix for the make_names function in helper-quick-df.r. I did not test, but I do not think there will be any difference in computation time, especially since the modification is executed on a primitive function, sum.

Example data

test_df <-
structure(list(health = structure(c(3L, 2L, 3L, 2L, 3L, 1L, 2L,
2L, 2L, 1L, NA, NA, 2L, 2L, 2L, 3L), .Label = c("very good",
"good", "fair", "poor", "very poor"), class = "factor"), age = c(30,
30, 30, 30, 30, 30, 30, 30, 30, 40, 40, 40, 40, 40, 40, 40)), .Names = c("health",
"age"), row.names = c("760", "761", "762", "763", "764", "765",
"766", "767", "768", "769", "770", "771", "772", "773", "774",
"775"), class = "data.frame")

before patch:

> ddply(test_df, "age", .fun= function(x) table(x$health, useNA="always"))
Error in seq_len(sum(nm == "")) :
  argument must be coercible to non-negative integer

after patch:

> ddply(test_df, "age", .fun= function(x) table(x$health, useNA="always"))
age very good good fair poor very poor NA
1  30         1    5    3    0         0  0
2  40         1    3    1    0         0  2

patch:

--- helper-quick-df.r   2011-10-31 01:40:53.000000000 -0400
+++ helper-quick-df.r.sk        2011-11-06 20:11:04.074707068 -0500
@@ -24,6 +24,6 @@
     nm <- rep("", length = length(x))
   }

-  nm[nm == ""] <- paste(prefix, seq_len(sum(nm == "")), sep = "")
+  nm[nm == ""] <- paste(prefix, seq_len(sum(nm == "", na.rm = TRUE)), sep = "")
   nm
-}
\ No newline at end of file
+}

Scott

[hadley]

Thanks Scott - would mind having a go at creating a formal pull request? That way you could also include a test and a comment in the NEWS file describing the improvement.

[scottkosty]

Sure, Hadley -- I'll do that within a week.