[Eeglablist] plotting ERPs with standard error shades (A T)

Laurens R Krol lrkrol at gmail.com
Thu Feb 7 03:00:24 PST 2019


Dear Angel,

    pop_comperp (Plot -> Sum/Compare ERPs) is capable of plotting standard
deviations, but only when given multiple datasets: it'll take the standard
deviation between the mean ERPs of each dataset, thus, with a sample a size
equalling the number of datasets that are averaged together -- which is
probably what you're looking for in a study.
    This option is greyed out when a study is loaded, but it still works
from the command line, if all study datasets are stored in memory. If they
are ordered consistently, you can use the indices in ALLEEG to refer to
specific conditions. For example, for a study of 20 participants with 8
conditions each, all loaded in the same order as separate datasets, indices
[1:8:160] should contain the first condition's datasets, [2:8:160] the
second, etc.

    But, you asked for standard error, not standard deviation, and a
shading effect, not lines.

    I've created an ERP plotting function that can plot the standard error
of the mean, and can do this for single datasets as well as combinations of
datasets. See https://github.com/lrkrol/plot_erp, set 'plotstd' to 'fill',
and perhaps look into the argument 'avgmode' depending on what you need.

    While we're at it, if anyone's still reading: are there any arguments
for deciding between showing standard *deviation* and standard *error*, or
any other measures of spread, for ERP plots? I was considering implementing
other measures in plot_erp.

Cheers,

    Laurens
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