How to calculate mean of column, then paste mean value as row value in another data frame in R?

Question

I have 36 data frames that each contain columns titled "lon", "lat", and "bottom_temp". Each different data frame represents data from a year between 1980 and 2015. I have a seperate dataframe called "month3_avg_box" that contains two columns: "year" and "avg_bottom_temp". The year column of the "month3_avg_box" data frame contains one row for each year between 1980-2015. I would like to find the average value of each "bottom_temp" column in each of the 36 data frames I have, and place each mean in the corresponding row of the new "month3_avg_box" data frame I have. I will write a mini example of what I'd like:

1980_df:
lon      lat      bottom_temp
-75.61   39.1      11.6
-75.60   39.1      11.5
-75.59   39.1      11.6
-75.58   39.1      11.7

(mean of bottom_temp column for 1980_df = 11.6)

1981_df:
lon      lat      bottom_temp
-75.57   39.1      11.9
-75.56   39.1      11.9
-75.55   39.1      12.0
-75.54   39.1      11.8

(mean of bottom_temp column for 1981_df = 11.9)

1982_df:
lon      lat      bottom_temp
-75.57   39.1      11.6
-75.56   39.1      11.7
-75.55   39.1      11.9
-75.54   39.1      11.2

(mean of bottom_temp column for 1982_df = 11.6)

Now, I'd like to take these averages and put them into my "month3_avg_box" data frame so it looks like:

month3_avg_box:
Year      Avg_bottom_temp
1980        11.6
1981        11.9
1982        11.6

Does this make sense? How can I do this?

Answer 1

We may get the datasets in a list

library(dplyr)
library(stringr)
lst(`1980_df`, `1981_df`, `1982_df`) %>%
    bind_rows(.id = 'Year') %>%
    group_by(Year = str_remove(Year, '_df')) %>%
    summarise(Avg_bottom_temp = mean(bottom_temp))

-output

# A tibble: 3 × 2
  Year  Avg_bottom_temp
  <chr>           <dbl>
1 1980             11.6
2 1981             11.9
3 1982             11.6

data

`1980_df` <- structure(list(lon = c(-75.61, -75.6, -75.59, -75.58), lat = c(39.1, 
39.1, 39.1, 39.1), bottom_temp = c(11.6, 11.5, 11.6, 11.7)), class = "data.frame", row.names = c(NA, 
-4L))
`1981_df` <- structure(list(lon = c(-75.57, -75.56, -75.55, -75.54), lat = c(39.1, 
39.1, 39.1, 39.1), bottom_temp = c(11.9, 11.9, 12, 11.8)), class = "data.frame", row.names = c(NA, 
-4L))
`1982_df` <- structure(list(lon = c(-75.57, -75.56, -75.55, -75.54), lat = c(39.1, 
39.1, 39.1, 39.1), bottom_temp = c(11.6, 11.7, 11.9, 11.2)), class = "data.frame", row.names = c(NA, 
-4L))