将图表转换为R中的数据框架

Question

So a while back (6 months+) I saw a blog post where the author took a line graph someone had posted on the internet, fed the image into R, and used a function to convert the image into a data frame.

I've looked everywhere, and I can't seem to find this blog post (even though I'm sure I bookmarked it). So I was wondering if any of you had also read said blog post, or if someone knew of a quick and easy way to convert a line graph to a data frame in R?

Answer 1

Was this it? I searched for "R digitize plot". The package used is " ReadImages ". For completeness, the steps listed were (see link):

library(ReadImages) #Load package
mygraph <- read.jpeg('plot.jpg') #Import image
plot(mygraph) # Plot the image
calpoints <- locator(n=4,type='p',pch=4,col='blue',lwd=2) # Calibrate the plot by selecting known coordinates
data <- locator(type='p',pch=1,col='red',lwd=1.2,cex=1.2) # Collect the data points in a dataframe

Answer 2

When you say 'the image as a data frame', do you mean you want to get back to the original data that made the line?

It's not R, but I've used Engauge Digitizer for this sort of thing:

http://digitizer.sourceforge.net/

Answer 3

As i write this, the digitize package and the ReadImages package are no longer available for R 3.0.2. Engauge Digitizer is a good option but if you still want to do this sort of thing in R, take a loook at http://rscriptsandtips.blogspot.no/

Answer 4

Also look at the updateusr function in the TeachingDemos package. Once you have the image displayed as in Benjamin's post, you can use the updateusr function with the known points to change the user coordinates so that then the results from the locator function do not need any additional transformation.

Answer 5

You can also use im2graph to convert graphs to data. It's free and available of Windows and Linux ( http://www.im2graph.co.il ).