npp | R Documentation |
A plotting routine producing non-parametric analogues of the IRF not unlike
those in Jim Ramsay's TestGraf program. The curves are produced by a kernel
binomial regression of the actual responses to an item on some estimates of
the latent variable, by courtesy of package sm
.
npp( resp, x, items, from = -4, to = 4, co = 1, main = "Non-parametric response function", add = FALSE, bands = FALSE, label = FALSE )
resp |
A matrix of responses: persons as rows, items as columns, entries are either 0 or 1, no missing data |
x |
The values of the latent variable ("ability") for the same persons
whose responses are given in |
items |
An index to the items (columns of |
from |
Lower limit for ability on the plot. Default is -4. |
to |
Upper limit for ability on the plot. Default is 4. |
co |
The colour of the curves. Default is 1 for black. Use |
main |
The main title of the plot, given that |
add |
When |
bands |
When |
label |
When |
Ivailo Partchev
James O. Ramsay (2000). TestGraf: A program for the graphical analysis of multiple choice test and questionnaire data. McGill University, Montreal, Canada
qrs
, irf
, plot.irf
# plot items 1:5 in different colours, label npp(Scored, items=1:5, co=NA, label=TRUE) # For item 7, compare npp with the 2PL parametric IRF npp(Scored, items=7, bands=TRUE) plot(irf(ip=Scored2pl, items=7), co=3, add=TRUE)
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