将数据框中的值替换为同一 dataframe 中另一列的对应值

Question

This my data frame df

country    cum_cases      v_dt_date

MX             3              16
MX             2              18
MX             6              32

If the value in the column v_dt_date == 16 I want to change the value of the row in cum_cases to 10.

I tried with this: df$cum_cases[df$v_dt_date == 16]<-10 But is not working.

Desired output

country    cum_cases      v_dt_date

MX             10             16
MX             2              18
MX             6              32

Answer 1

Here are a couple options:

# Direct assignment - nice and efficient
df$cum_cases[df$v_dt_date == 16] <- 10

# ifelse - generalizes well to more complex cases, 
# e.g., nested conditions, more complex results
df$cum_cases <- with(df, ifelse(v_tdt_date == 16, 10, cum_cases))