building blocks of trials

[luciano basso]

Hi  Gene,

Thank you for your attention.

These data are from a study of motor learning, ok.
Each subject performs several trials. Every trials has several
components (3 components in this example).

I need to divide the various trials in 3 blocks. After generating an
average of these blocks.

The problem is that each individual has different number of trials.
The number of trials for each subject will be different.

I created a more simpler example. I added the variable block. This is
what I want to automate.


subject phase trial block
1       1       1       1
1       1       1       1
1       1       1       1
1       1       2       1
1       1       2       1
1       1       2       1
1       1       3       2
1       1       3       2
1       1       3       2
1       1       4       2
1       1       4       2
1       1       4       2
1       1       5       3
1       1       5       3
1       1       5       3
1       1       6       3
1       1       6       3
1       1       6       3
1       2       1       1
1       2       1       1
1       2       1       1
1       2       2       1
1       2       2       1
1       2       2       1
1       2       3       2
1       2       3       2
1       2       3       2
1       2       4       2
1       2       4       2
1       2       4       2
1       2       5       2
1       2       5       2
1       2       5       2
1       2       6       3
1       2       6       3
1       2       6       3
1       2       7       3
1       2       7       3
1       2       7       3
1       2       8       3
1       2       8       3
1       2       8       3
2       1       1       1
2       1       1       1
2       1       1       1
2       1       2       1
2       1       2       1
2       1       2       1
2       1       3       2
2       1       3       2
2       1       3       2
2       1       4       2
2       1       4       2
2       1       4       2
2       1       5       3
2       1       5       3
2       1       5       3
2       1       6       3
2       1       6       3
2       1       6       3
2       2       1       1
2       2       1       1
2       2       1       1
2       2       2       1
2       2       2       1
2       2       2       1
2       2       3       1
2       2       3       1
2       2       3       1
2       2       4       2
2       2       4       2
2       2       4       2
2       2       5       2
2       2       5       2
2       2       5       2
2       2       6       2
2       2       6       2
2       2       6       2
2       2       7       3
2       2       7       3
2       2       7       3
2       2       8       3
2       2       8       3
2       2       8       3
2       2       9       3
2       2       9       3
2       2       9       3


In the above example, note that:
The first subject has 6 trials in the first phase and 8 trials in the
second phase. When divided by 3 blocks were obtained: the first phase,
3 blocks with 2 tries each, and Phase 2 has 3 blocks with 3 trials for
the last 2 blocks and trials to block the first. The new variable
block was done by hand, what need is automating it.

Thanks..

Luciano Basso

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[Maguin, Eugene]

Luciano,

I have question about your problem. I understood you to say that you wanted
to group the trials into groups of 3 trials. However, in your example data
subject 1, phase 1 has 6 trials but 3 blocks of 2 trials. According to your
rule, shouldn't there be 2 blocks?

After looking at the data for awhile, I think I finally understand how to do
what you want--maybe. The maximum value of trial for a subject-phase is the
key element, I think. I want to make sure I understand how you want to group
trials based on the maximum number of trials. So, is the following table
correct?

Max trials  number of blocks
1            1
2            1
3            1
4            2 (3 and 1 or 2 and 2)???
5            2
6            2
7            3 (3 and 3 and 1) OR 2 (3 and 2 and 2)???
8            3 (3 and 3 and 2)
9            3

Please edit the table to indicate the correct number of blocks for a given
number of trials.

Gene Maguin

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[Maguin, Eugene]

This is the code I sent separately to Luciano for his evaluation. I do not
include his sample data here in the interests of space. I supplemented his
data with the creation of another case.

Gene Maguin


format subject phase trial block(f2.0).

crosstabs trial by subject by phase.


delete variables block.

compute component=1.
if (trial eq lag(trial)) component=lag(component)+1.
format component(f1.0).

*  multipliers will need to be adjusted to fit number of trials.
compute SubjectPhaseTrial=subject*1000+phase*100+trial.
format subjectphasetrial(f4.0).
execute.
delete variables subject phase trial.

casestovars /id=subjectphasetrial.

*  divisor will need to be adjusted to fit number of trials.
compute subjectphase=trunc(subjectphasetrial/100).
format subjectphase(f2.0).

aggregate outfile=* mode=addvariables/break=subjectphase/recs=nu.

*  always want to have three blocks of trials.
compute nperblock=recs/3.
format nperblock(f4.2).

*  multiplier will need to be adjusted to fit number of trials.
compute trial=subjectphasetrial-100*subjectphase.
format trial(f2.0).

compute block=trunc((trial+rnd(nperblock)-1)/rnd(nperblock)).
if (block eq 4) block=3.  /*  special correction.
format block(f2.0).

compute subject=trunc(subjectphase/10).
compute phase=subjectphase-subject*10.
execute.
format subject phase(f1.0).

delete variables SubjectPhaseTrial subjectphase recs nperblock.

varstocases /make component from component.1 component.2 component.3.

crosstabs trial by subject by phase.

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