replacing percentage of values in data frame

I've been looking for how to change a certain percentage of values in a data
frame, but I've been struggling to find information in R.

For example:

#################example data##############

data

? ? ?V1 ? ?V2 ? ?V3 ?V4 V5 ?V6 V7
1 ? chr1 ? 500 ? 500 CHH ?0 0.5 ?+
2 ? chr1 ? 550 ? 550 CHH ?0 0.0 ?+
3 ? chr2 ? 700 ? 700 CHH ?0 0.0 ?+
4 ? chr2 ?1000 ?1000 CHH ?0 0.0 ?+
5 ? chr3 ? 100 ? 100 CHH ?0 0.0 ?+
6 ? chr4 ? 450 ? 450 ?CG ?0 0.0 ?+
7 ? chr5 ? 450 ? 450 CHH ?0 0.0 ?+
8 ? chr5 50034 50034 CHG ?0 0.0 ?+
9 ? chr7 50055 50055 CHG ?0 0.0 ?+
10 chr10 50063 50063 CHH ?0 0.0 ?+

dput(data)

structure(list(V1 = structure(c(1L, 1L, 3L, 3L, 4L, 5L, 6L, 6L,
7L, 2L), .Label = c("chr1", "chr10", "chr2", "chr3", "chr4",
"chr5", "chr7"), class = "factor"), V2 = c(500L, 550L, 700L,
1000L, 100L, 450L, 450L, 50034L, 50055L, 50063L), V3 = c(500L,
550L, 700L, 1000L, 100L, 450L, 450L, 50034L, 50055L, 50063L),
? ?V4 = structure(c(3L, 3L, 3L, 3L, 3L, 1L, 3L, 2L, 2L, 3L), .Label =
c("CG",
? ?"CHG", "CHH"), class = "factor"), V5 = c(0L, 0L, 0L, 0L,
? ?0L, 0L, 0L, 0L, 0L, 0L), V6 = c(0.5, 0, 0, 0, 0, 0, 0, 0,
? ?0, 0), V7 = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
? ?1L), .Label = "+", class = "factor")), .Names = c("V1", "V2",
"V3", "V4", "V5", "V6", "V7"), class = "data.frame", row.names = c(NA,
-10L))

############################

Say for instance, I'd like to change 20% of values in column 6 to '1'
instead of zero or whatever value may be currently present. How would I
approach this?

I am working with a large data frame and I need to replace values in one of
the columns for 10-20% of the entire dataset. I hope what I am trying to
convey is understandable to you.

--
View this message in context: http://r.789695.n4.nabble.com/replacing-percentage-of-values-in-data-frame-tp3920484p3920484.html
Sent from the R help mailing list archive at Nabble.com.