How to run a block of code like using if and else statements or a replacement to if-else statement

R noob here again. I want to prompt the user and according to user's choice I want to execute a block code. So example;

answer <- readline(prompt = " Enter a, b or c: ")
if (answer == "a") {
    library("igraph")
    variable <- graph_from_data_frame(d=links, vertices=nodes, directed=T)
    variable
    plot(variable, edge.arrow= .5, vertex.frame.color = "#ffffff")

} else if (answer == "b") {
      #do something else like above
} else {
      #do something different than everything above 
}

This didn't work for me, switch cases didn't also work. Is there a solution for this kind of a problem? This also gave me: Error: unexpected '}' in " }"

I am pretty sure I didn't do any mistakes with my brackets.