populating data based on column/rownames with uneqal row number [duplicate] - r

Question

This question already has answers here:
Match values in data frame with values in another data frame and replace former with a corresponding pattern from the other data frame
(3 answers)
Closed 4 years ago.
I need to populate empty data frame with values based on values in first columns (or alternatively row names it is the same for me in this case). So here are three objects:
set.seed=11
empty_df=data.frame(cities=c("New York","London","Rome","Vienna","Amsterdam"),
col.a=rep(NA,5),
col.b=rep(NA,5),
col.c=rep(NA,5))
values=rnorm(4,0,1)
to_fill=data.frame(cities=c("New York","London","Vienna","Amsterdam"),
col.a=values)
desired_output=data.frame(cities=c("New York","London","Rome","Vienna","Amsterdam"),
col.a=c(values[1],values[2],NA,values[3],values[4]),
col.b=rep(NA,5),
col.c=rep(NA,5))
First column (it can be converted to row names, both solutions using row names or first column with city name is fine) consists some cities i like to visit and other some unspecified values. First is df I want to fill with values and its output is:
cities col.a col.b col.c
1 New York NA NA NA
2 London NA NA NA
3 Rome NA NA NA
4 Vienna NA NA NA
5 Amsterdam NA NA NA
Second is object I want put INTO empty df and as you can see it is missing one row (with "Rome"):
cities col1
1 New York 0.55213218
2 London 0.98907729
3 Vienna 1.11703741
4 Amsterdam -0.04616725
So now I want to put this inside empty df leaving NA in row which dose not match:
cities col.a col.b col.c
1 New York -0.62731870 NA NA
2 London -1.80206612 NA NA
3 Rome NA NA NA
4 Vienna -1.73446286 NA NA
5 Amsterdam -0.05709419 NA NA
I was trying to use simplest merge solution like this: merge(empty_df,to_fill, by="cities"):
cities col.a.x col.b col.c col.a.y
1 Amsterdam NA NA NA -0.05709419
2 London NA NA NA -1.80206612
3 New York NA NA NA -0.62731870
4 Vienna NA NA NA -1.73446286
And when i tried desired_output$col.a=merge(empty_df,to_fill, by="cities") error occurred(replacement has 4 rows, data has 5). Is there any simple solution to do this that can be put in for loop or apply?

Answer 1

We can use match:
empty_df$col.a <- to_fill$col.a[match(empty_df$cities, to_fill$cities)]
empty_df;
# cities col.a col.b col.c
#1 New York 1.5567564 NA NA
#2 London -0.6969401 NA NA
#3 Rome NA NA NA
#4 Vienna 1.3336636 NA NA
#5 Amsterdam 0.7329989 NA NA
We fill col.a of empty_df with col.a values from to_fill by matching cities from empty_df with cities from to_fill.