How to use ifelse for specific column?

[farah]

Hi. I have created the following in R

net<-data.frame(source=c("A","A","B","C","D","D","E"),target=c("B","D","A","A","C","E","D"))

library(igraph)
graph<-graph_from_data_frame(d=net,directed=TRUE)
plot(graph)
adj<-get.adjacency(graph,sparse=FALSE)

ifelse(adj[,c(1)]==1,x=sum(adj[,c(1)]-adj[c(1),],x=0))

I want to calculate this equation:

How do I do that? Thank you in advance!

[pieterjanvc]

Hi,

Welcome to the RStudio community!

The ifelse function does not wrap the whole statement, but just the columns you like to work on like this

adj[,c(1)] = ifelse(adj[,c(1)]==1, sum(adj[,c(1)]-adj[c(1),]),0)

All it does is take a vector of T/F, then returns values from two other vectors depending on the case. It's also possible to just return one value for either T or F, as you are doing here (the sum or 0).

Example:

# Vector input, one possible true of false answer
ifelse((1:5 %% 2) == 0, "even", "odd")
#> [1] "odd"  "even" "odd"  "even" "odd"

# Vector input, pick corresponding index value from true or false vectors
ifelse((1:5 %% 2) == 0, letters[1:5], LETTERS[1:5])
#> [1] "A" "b" "C" "d" "E"

^{Created on 2022-04-18 by the reprex package (v2.0.1)}

My answer if just helping you fix your current error, but I'm not 100% sure if your code captures the function one you provided, so please check this.

Hope this helps,
PJ

[farah]

Thank you sm! The solution you give does fix the error. Unfortunately, like you said, your code does not capture the function I provided. It's ok. I'll figure it out.