Line plot in r ignoring missing data

I have a dataset where missing data is represented as -999. The data goes from 0 to 1. I would like to plot the data as a line plot, but I don't want the valid numbers to connect to the missing data. For example if I have

x = c(0.29, 0.3, -999, 0.31, 0.4)

I want the line to go from 0.29 to 0.3, break at the missing data, and start again between 0.31, 0.4.

Assuming the above data is in file x.txt, I tried to do the following:

x1 = read.table('x.txt', na.strings=c("-999."))
plot(x1, type='l')

but it doesn't do what I w开发者_开发知识库ant.

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Replace the -999 with NA:

is.na(x) <- (x == -999)
plot(x, type="l")

Is that what you want?

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Another way of changing -999 to NA is:

x[x==-999] = NA
plot(x, type="l")

This gives the same results as @Joshua's nice answer, but may be clearer if you are new to R.

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You don't say what it does and how that does not match with what you want.

One problem you could be having is that read.table returns a data frame, so in your code it is trying to plot the data frame, not the x column within the data frame. What happens depends on how many columns your data frame ends up with (something that we cannot guess from your example).

If there are exactly 2 columns then a regular scatterplot is created (but options may not pass through correctly). If x1 has only one column then a strip plot is created which is quite different from the scatterplot created when you give a single vector to the plot.default command.

So maybe

plot( x1[[1]], type='l' ) 

or something like that is what you want.

If not, show us what your data frame looks like after reading it in:

summary(x1)
str(x1)