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ind_1
2006 Apr 13
1
Subset rows over multiple columns
I have a data frame where I need to subset certain rows before I compute
the mean of another variable. However, the value that I need to subset
by is found in multiple columns. For example, in the data below the
value R0000160 is found in the first and second columns (itd_1 and
itd_45). These data are student responses to multiple choice test items
from a computer adaptive test. So, the variable itd_1 denotes that item
i was presented to student k in position t and then the variable
righta_a and righta_b denotes a correct (1) or incorrect response to
that item when i...