NeuroAnalyzer tutorials: Analyze EEG (3)

Often it is required to analyze only a segment of data, e.g. part of the spectrogram or topographical map.

First, a matrix data has to be prepared, e.g.:

# data at 2560 sample across 19 channels
s = eeg.data[1:19, 2560, 1]
# prepare planar interpolation
z, x, y = plinterpolate(s, locs=locs, ch=1:19)
# preview
Plots.heatmap(x, y, z)

Next, a segment of interest has to be extracted:

seg = iselect_seg(z)

(!) Place the selection corners using left clicks. Middle click undoes the last action. Press Enter when ready or ctrl-q to cancel and close the window.

Output:

(35, 37, 63, 63)

These are coordinates of the left upper corner (row and column) and bottom right corner (row and column) of the segment.

To select a circular segment, use c=true parameter:

seg = iselect_seg(z, c=true)

For circular segment coordinates are: center (row and column) and peripheral point (row and column).

To extract the segment data:

m = seg_extract(z, seg)

Output:

29×27 Matrix{Float64}:
 0.449312  …  0.488266
 ⋮         ⋱  ⋮         
 0.640943     0.659986

If you need the segment to be extracted as a vector, use the v=true parameter.

v = seg_extract(z, seg, v=true)

Output:

783-element Vector{Float64}:
 0.44931180669912063
 ⋮
 0.6177368628322506

If segment is circular, use c=true parameter when extracting:

m = seg_extract(z, seg, c=true)

(!) Circular segments are always returned as vectors.

Alternatively, use iselect_seg() with extract=true parameter.

seg = iselect(z, extract=true, v=true)

or combine these two functions:

seg = seg_extract(z, iselect_seg(z))