Plot the total information with solid line and expected SEE function (dashed line) in the same graph

[Yuen Wan Ho]

Hi everyone, 

I looked at the manuel for mirt and got some ideas about plotting. What command or script I should type when I wish to plot  the total information with solid line and expected SEE function (dashed line) in the same graph?

Thanks alot!

Yuen Wan

[Phil Chalmers]

Something like plot(mod, type = 'infoSE')?

Phil

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[Yuen Wan Ho]

Hi Phil,

The code that can plot both total information function and expected SEE function (for example, the one as shown in the attachment (Toland, 2014, p.147)

Thanks!

Yuen Wan
Phil Chalmers於 2016年5月7日星期六 UTC+8上午4時21分57秒寫道：

[Phil Chalmers]

You probably can't do this exact plot with the built in plots, but see the lower level components that make them up. E.g., testinfo(). Then just build the plot yourself from the respective pieces. Cheers.

Phil

[Yuen Wan Ho]

Hi Phil,

Thank you so much for your quick response and advice :)

Yuen Wan

Phil Chalmers於 2016年5月9日星期一 UTC+8下午12時50分51秒寫道：

[Phil Chalmers]

As a follow up, this seems to be what you are after (minus the legend).

library(mirt)

mod <- mirt(Science, 1)

Theta <- matrix(seq(-3,3,length.out=1000))

d = data.frame(Theta, I=testinfo(mod, Theta))

d$SE <- sqrt(1/d$I)

par(mar = c(5,5,2,5))

with(d, plot(Theta, I, type="l",las=2, lwd=2, xlab = expression(theta),

ylab = expression(Information (theta))))

par(new = T)

with(d, plot(Theta, SE, type = 'l', axes=F, lty=2, ylab=NA, lwd=2))

axis(side = 4, las=2)

mtext(side = 4, line = 3, expression(SEE(theta)))

 

Phil

[Phil Chalmers]

Updated (xlab was written 2x in last message).

library(mirt)

mod <- mirt(Science, 1)

Theta <- matrix(seq(-3,3,length.out=1000))

d = data.frame(Theta, I=testinfo(mod, Theta))

d$SE <- sqrt(1/d$I)

par(mar = c(5,5,2,5))

with(d, plot(Theta, I, type="l",las=1, lwd=2, xlab = expression(theta),

ylab = expression(Information (theta))))

par(new = T)

with(d, plot(Theta, SE, type = 'l', axes=F, lty=2, ylab=NA, lwd=2, xlab=NA))

axis(side = 4, las=2)

mtext(side = 4, line = 3, expression(SEE(theta)))

 

Phil