CODEWITHSUNDEEP
rplot
user27976
user27976

Reputation: 903

Plot points with 3 different colors

I have the following two columns as part of my dataframe and a function below:

X
705.7553
789.2789
689.7431
559.8025
629.9365
564.9095

Y
-0.0596123270783229
 0.644158691971081
-0.433854284204926
-0.365746109442603
 0.566685929975495
 0.398462720589891

Function:

plotM<- function( all.res, m, u ) {
  plot(data$X, data$Y,
       log="x", pch=20, cex=0.7,
       col = ifelse( data$Y < m, "red", "black" ), 
       xlab = "Y", ylab = expression(Log[2]~Fold~Change))
}

Function call:

plotM(data, .05)  # plots a graph with red points when  data$Y < m and black when data$Y > m

But I'm interested in the following:

plotM(data, 0.05, 0.1 )  #  to plot a graph with red points when data$Y < m, green when data$Y > u, and the rest colored black

Can anyone help please? Thanks

Upvotes: 1

Views: 3597

Answers (2)

Jaap
Jaap

Reputation: 83225

You can rewrite your function as follows (utilizing ggplot2, for baseplot: see below):

plotM <- function(data, m, u){
  data$cols <- ifelse(data$Y < m, "1", ifelse(data$Y > u, "2", "3"))
  ggplot(data, aes(x = X, y = Y, color = cols)) +
    geom_point(size=3) + 
    scale_color_manual(breaks = c(1,2,3), values = c("red","green","black"),
                       labels = c("red","green","black")) +
    theme_bw()
}

plotM(data, 0.05, 0.4)

with your data this gives: enter image description here

With the baseplot your function will look like:

plotBase <- function(data,m,u){
  data$cols <- ifelse(data$Y<m,"red",ifelse(data$Y>u,"green","black"))
  plot(data$X, data$Y, col=data$cols, pch=20)
}

plotBase(data,0.05,0.4)

which gives: enter image description here

Upvotes: 3

Anders Ellern Bilgrau
Anders Ellern Bilgrau

Reputation: 10223

We first generate some toy data:

set.seed(1)
X <- rnorm(100)
Y <- rnorm(100)

You can do something like:

m <- c(-Inf, -0.5, 0.5, Inf)  # Specify your cut points, here -0.5 and 0.5
cols <- cut(Y, breaks = m)
plot(X, Y, col = cols)

We here use the fact that cut returns a factor, and use the numeric values of the levels as colors. You could also write something like:

cols <- as.character(cut(Y, breaks = m, labels = c("Black", "Red", "Green")))

to construct the colours.

Alternatively, you can use nest ifelse. I.e.

plot(X, Y, col = ifelse(Y < -0.5, "Red", ifelse(Y > 0.5, "Green", "Black")))

plot(X, Y)

Upvotes: 4

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