R: returning row value when certain number of columns reach certain value

Question

Return row value when certain number of columns reach certain value from the following table

    V1   V2   V3   V4   V5   V6   V7   V8   V9   V10
1   3.93    3.92    3.74    4.84    4.55    4.67    3.99    4.10    4.86     4.06
2   4.00    3.99    3.81    4.90    4.61    4.74    4.04    4.15    4.92     4.11
3   4.67    4.06    3.88    5.01    4.66    4.80    4.09    4.20    4.98     4.16
4   4.73    4.12    3.96    5.03    4.72    4.85    4.14    4.25    5.04     4.21
5   4.79    4.21    4.04    5.09    4.77    4.91    4.18    4.30    5.10     4.26
6   4.86    4.29    4.12    5.15    4.82    4.96    4.23    4.35    5.15     4.30
7   4.92    4.37    4.19    5.21    4.87    5.01    4.27    4.39    5.20     4.35
8   4.98    4.43    4.25    5.26    4.91    5.12    4.31    4.43    5.25     4.38
9   5.04    4.49    4.31    5.30    4.95    5.15    4.34    4.46    5.29     4.41
10   5.04    4.50    4.49    5.31    5.01    5.17    4.50    4.60    5.30     4.45
11   ...
12   ...

As an output, I need a data frame, containing the % reach of the value of interest ('5' in this example) by V1-V10:

Rownum   Percent
1   0
2   0
3   10
4   20
5   20
6   20
7   33
8   33
9   40
10  50

Many thanks!

Answer 1

If your matrix is mat:

cbind(1:dim(mat)[1],rowSums(mat>5)/dim(mat)[2]*100)

Answer 2

As far as it's always about 0 and 1 with ten columns, I would multiply the whole dataset by 10 (equals percentage values in this case...). Just use the following code:

# Sample data
set.seed(10)

data <- as.data.frame(do.call("rbind", lapply(seq(9), function(...) {
  sample(c(0, 1), 10, replace = TRUE)
})))
rownames(data) <- c("abc", "def", "ghi", "jkl", "mno", "pqr", "stu", "vwx", "yza")

# Percentages
rowSums(data * 10)

# abc def ghi jkl mno pqr stu vwx yza 
#  80  40  80  60  60  10  30  50  50

Answer 3

Ok, so now I believe you want to get the percentage of values in each row that meet some threshold criteria. You give the example > 5. One solution of many is using apply:

apply( df , 1 , function(x) sum( x > 5 )/length(x)*100  )
# 1  2  3  4  5  6  7  8  9 10 
# 0  0 10 20 20 20 30 30 40 50 

@Thomas' solution will be faster for large data.frames because it converts to a matrix first, and these are faster to operate on.