Plotting Simple Data in R


Question

I have a comma separated file named foo.csv containing the following data:

scale, serial, spawn, for, worker
5, 0.000178, 0.000288, 0.000292, 0.000300
10, 0.156986, 0.297926, 0.064509, 0.066297
12, 2.658998, 6.059502, 0.912733, 0.923606
15, 188.023411, 719.463264, 164.111459, 161.687982

I essentially have two questions:

1) How do I plot the first column (x-axis) versus the second column (y-axis)? I'm trying this (from reading this site):

data <- read.table("foo.csv", header=T,sep=",")
attach(data)
scale <- data[1]
serial <- data[2]
plot(scale,serial)

But I get this error back:

Error in stripchart.default(x1, ...) : invalid plotting method

Any idea what I'm doing wrong? A quick Google search reveals someone else with the same problem but no relevant answer. UPDATE: It turns out it works fine if I skip the two assignment statements in the middle. Any idea why this is?

The second question follows pretty easily after the first:

2) How do I plot the first column (x-axis) versus all the other columns on the y-axis? I presume it's pretty easy once I get around the first problem I'm running into, but am just a bit new to R so I'm still wrapping my head around it.

1
19
7/23/2009 1:09:11 PM

Accepted Answer

You don't need the two lines:

scale <- data[1]
serial <- data[2]

as scale and serial are already set from the headers in the read.table.

Also scale <- data[1] creates an element from a data.frame

  data[1]
1     5
2    10
3    12
4    15

whereas scale from the read.table is a vector

5 10 12 15

and the plot(scale, serial) function expects vector rather than a data.frame, so you just need to do

plot(scale, serial)

One approach to plotting the other columns of data on the y-axis:

plot(scale,serial, ylab="")
par(new=TRUE) 
plot(scale,spawn,axes=F, ylab="", type="b")
par(new=TRUE) 
plot(scale,for., axes=F, ylab="", type="b")
par(new=TRUE) 
plot(scale,worker,axes=F, ylab="", type="b")

There are probably better ways of doing this, but that is beyond my current R knowledge....

12
5/18/2009 9:44:26 AM

In your example,

plot(scale, serial) 

won't work because scale and serial are both data frames, e.g.

class(scale)
[1] "data.frame"

You could try the following and use points(), once the plot has been generated, to plot the remaining columns. Note, I used the ylim parameter in plot to accommodate the range in the third column.

data <- read.csv('foo.csv', header=T)
plot(data$scale, data$serial, ylim=c(0,750))
points(data$scale, data$spawn, col='red')
points(data$scale, data$for., col='green')
points(data$scale, data$worker, col='blue')

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