GGPLOT - DIF analysis (Is it possible to change the plot?)

[Cursos Psi]

Dear Dr. Phil, 

I'm trying to use ggplot to plot a DIF analysis I conducted with my dataset (two groups: male and females). I've found your code here and it helped me a lot. Unfortunately, I'm afraid I could not use this script to plot DIF analysis when I have two groups (That is my case). Could you please help me (and, probably, other mirt users) ?

I want to transform this output:

plot(mod_metric, type='info')

To something like this output

plt <- plot(mod_metric, type='info') #store the object

plt$panel.args

pltdata <- data.frame(lapply(plt$panel.args, function(x) do.call(cbind, x))[[1]])

ggplot(pltdata, aes(x, y)) + 

  geom_line(size = 1.5) + 

  labs(x="ability", y="I(Theta)")

I know this question is much more a programming question than a mirt question, but I've tried to ask on stackoverflow and they did not accepted it.

Thanks.

[Cursos Psi]

Dear Dr Phil,

I've also tried this code here : https://groups.google.com/forum/#!searchin/mirt-package/data.frame(Theta$2C$20I$3Dtestinfo(%7Csort:date/mirt-package/vitkT8J9AHw/g8jFlDKTBwAJ

Thank you

[Phil Chalmers]

It looks like you missed the grouping variable within the defined data. You'd need to locate and pull that out as well in order to properly map the functions (here it's clearly that lines are being drawn from one group and then the next). HTH.

Phil

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[Cursos Psi]

Dear Dr. Phil, 

thanks. I've realized I forgot this grouping variable, but I don't know how to do that. Do you have any code or tutorial that I can learn from ?

If you don't, that's ok and, again, thanks much for all support you always provide.

Phil

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[Phil Chalmers]

If you check out the structure of the lattice plot (via str(your_plot)) you should be able to locate a list element corresponding to the grouping variable. Lattice must have stored it *somewhere*, otherwise it too would have  it's plot look like yours. Try digging around for it in the object structure, and let us know if you can locate it. Cheers.

Phil

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[Cursos Psi]

Ok!

I'll do that! 

Thank you