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Quantile-Quantile (QQ) Plot
Posted: Sat Mar 31, 2012 4:33 am
by ac_1
A simple question: is there a QQ-plot graphical procedure in RATS i.e. quantiles (fractiles) of sample data may be compared graphically against quantiles of a base (normal, t, etc) distribution ?
Re: Quantile-Quantile (QQ) Plot
Posted: Mon Apr 02, 2012 3:58 am
by IRJ
The QPLOT procedure (QPLOT.src) does a QQ plot (it allows for a normal or exponential distribution).
Re: Quantile-Quantile (QQ) Plot
Posted: Mon Apr 02, 2012 10:01 am
by TomDoan
ac_1 wrote:A simple question: is there a QQ-plot graphical procedure in RATS i.e. quantiles (fractiles) of sample data may be compared graphically against quantiles of a base (normal, t, etc) distribution ?
What you're describing isn't a QQ plot but a Q plot, which, as was pointed out can be done with @QPLOT. QQ is a plot of two sample quantiles against each other on a scatter plot. If they're from the same distribution, the points should lie roughly on the y=x line. It's actually just a scattergram of sorted versions of the two series.
Code: Select all
all 200
set test1 = %ran(1.5)
set test2 = %ran(1.0)
*
* Q-Q plot
*
set x2 = test2
set x1 = test1
order x2
order x1
scatter(lines=||0.0,1.0||)
# x1 x2