Manipulate function within lapply

Question

This should be an easy question for someone out there...

I have a data frame that looks like this:

df1
 longitude lattitude 10000  5 1.5 1.4 1.3 1.2 1 0.5 0.1 0.001
0 -119.8304  34.44190   107 14   8   8   8   8 7   5   5     1
1 -119.6768  34.41962   107 19   5   5   5   5 5   3   2     1
2 -119.7162  34.41911   107 25   9   8   8   5 4   1   1     1
3 -119.7439  34.44017   107 22   7   7   6   5 5   2   1     1

Which was created by this code:

library(geosphere)

df1 <- data.frame(longitude=c(-119.8304, -119.6768, -119.7162, -119.7439, -120.4406, -119.5296, -120.4198, -119.8221, -119.7269, -120.4252, -120.4573, -120.4581),
              lattitude=c(34.44, 34.42, 34.42, 34.44, 34.64, 34.41, 34.94, 34.44, 34.44, 34.97, 34.65, 34.65))
boundary <- c(10000, 5, 1.5, 1.4, 1.3, 1.2, 1, 0.5, 0.1, 0.001)
names(boundary) <- boundary
df1 <- cbind(df1, lapply(boundary, function(x) rowSums(distm(df1, fun = distHaversine) / 1000 <= x)))

But I need the values in the data frame df1 to be manipulated such that the value in all the columns except latitude and longitude will get divided by pi*x^2 (pi times x squared). Can I use lapply in this case?

The output should be like:

df1
longitude lattitude    10000  5     1.5   1.4 1.3 1.2 1 0.5 0.1 0.001
0 -119.8304  34.44190   0     0.177 1.12  1.29 etc...   

Answer 1

We can use setdiff to get the names of the dataset except the 'longitude', 'lattitude' column. Then loop through the subset of columns, do the calculation, and update the dataset

j1 <- setdiff(names(df1), c("longitude", "lattitude"))
df1[j1] <- lapply(df1[j1], function(x) x/(pi*x^2))

---

Or we can use tidyverse

library(dplyr)
df1 %>%
     mutate_at(vars(-matches("longitude", "lattitude")), funs(./(pi*.^2)))