将数值向量中的值乘以数据帧中的特定值

Question

I have a numeric vector:

> dput(vec_exp)
structure(c(12.344902729712, 6.54357482855349, 17.1939193108764, 
            23.1029632631654, 8.91495023159554, 14.3259091357051, 18.0494234749187, 
            2.92524638658168, 5.10306474037357, 2.66645609602021), .Names = c("Arthur_1", 
                                                                              "Mark_1", "Mark_2", "Mark_3", "Stephen_1", "Stephen_2", 
                                                                              "Stephen_3", "Rafael_1", "Marcus_1", "Georg_1"))

and then I have a data frame like the one below:

        Name     Nr       Numb
1  Rafael      20.8337  20833.7
2  Joseph      25.1682  25168.2
3  Stephen     40.5880  40588.0
4  Leon       198.7730 198773.0
5  Thierry     16.5430  16543.0
6  Marcus      31.6600  31660.0
7  Lucas       39.6700  39670.0
8  Georg      194.9410 194941.0
9  Mark        60.1020  60102.0
10 Chris       56.0578  56057.8

I would like to multiply the numbers in numeric vector by the numbers from the column Nr in this data frame. Of course it is important to multiply the values by the name. It means that Mark_1 from numeric vector should be multiplied by the Nr = 60.1020 , same for Mark_2, and Stephen_3 by 40.5880 , etc.

Can someone recommend any easy solution ?

Answer 1

You could use match to match the names after extracting only the first part of the names of vec_exp , ie extract Mark from Mark_1 etc.

vec_exp * df$Nr[match(sub("^([^_]+).*", "\\1", names(vec_exp)), df$Name)]
# Arthur_1     Mark_1     Mark_2     Mark_3  Stephen_1  Stephen_2  Stephen_3   Rafael_1   Marcus_1    Georg_1 
#       NA  393.28193 1033.38894 1388.53430  361.84000  581.46000  732.59000   60.94371  161.56303  519.80162 

Arthur is NA because there's no match in the data.frame.

---

If you want to keep those entries without a match in the data as they were before, you could do it like this:

i <- match(sub("^([^_]+).*", "\\1", names(vec_exp)), df$Name)
vec_exp[!is.na(i)] <- vec_exp[!is.na(i)] * df$Nr[na.omit(i)]

This first computes the matches and then only multiplies those if they are not NA.

Answer 2

We can use base R methods. Convert the vector to a data.frame with stack , create a 'Name' column by removing the substring from 'ind' and merge with the data.frame ('df1'). Then, we can multiply the 'Nr' and the 'values' column.

d1 <- merge(df1, transform(stack(vec_exp), Name = sub("_.*", "", ind)), all.y=TRUE)
d1$Nr*d1$values

---

Or with dplyr , it is much more easier to understand.

library(dplyr)
library(tidyr)
stack(vec_exp) %>%
        separate(ind, into = c("Name", "ind")) %>%
        left_join(., df1, by = "Name") %>% 
         mutate(res = values*Nr) %>% 
        .$res
#[1]         NA  393.28193 1033.38894 1388.53430  361.84000  
#[6]    581.46000  732.59000   60.94371  161.56303  519.80162