r - adding rows to data.frame conditionally -

i have big data.frame of flowers , fruits in plant 30 years survey. want add zeros (0) in rows represent individuals in specific months plant did not have flowers or fruits (because seasonal species).

example:

year month flowers fruits 2004 6      25      2 2004 7      48      4 2005 7      20      1 2005 8      16      1 

i want add months not included values of 0 thinking in function recognize missing months , fill them 0.

thanks.

## x data frame gave in question  x <- data.frame(   year = c(2004, 2004, 2005, 2005),   month = c(6, 7, 7, 8),   flowers = c(25, 48, 20, 16),   fruits = c(2, 4, 1, 1) )  ## y data frame provide missing values, ## can replace 2004 , 2005 whatever desired ## time interval  y <- expand.grid(year = 2004:2005, month = 1:12)  ## final step fills in missing dates , replaces na's zeros  library(tidyr) x <- merge(x, y, = true) %>%   replace_na(list(flowers = 0, fruits = 0))  ## if don't want use tidyr, can alternatively  x <- merge(x, y, = true) x[is.na(x)] <- 0 

it looks this:

head(x, 10)  #    year month flowers fruits # 1  2004     1       0      0 # 2  2004     2       0      0 # 3  2004     3       0      0 # 4  2004     4       0      0 # 5  2004     5       0      0 # 6  2004     6      25      2 # 7  2004     7      48      4 # 8  2004     8       0      0 # 9  2004     9       0      0 # 10 2004    10       0      0