Extend an irregular sequence and add zeros to missing values

Question

I have a data frame with a sequence in \'col1\' and values in \'col2\':

col1 col2
2     0.02
5     0.12
9     0.91
13    1.13

I want to exp

Answer 1

We can use base R with merge and replace

transform(merge(data.frame(col1= 1:13), df, all.x=TRUE),
                      col2 = replace(col2, is.na(col2), 0))
#    col1 col2
#1     1 0.00
#2     2 0.02
#3     3 0.00  
#4     4 0.00
#5     5 0.12
#6     6 0.00
#7     7 0.00
#8     8 0.00
#9     9 0.91
#10   10 0.00
#11   11 0.00
#12   12 0.00
#13   13 1.13