Plotting cell array with empty cells - changing linespec

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Jared
Jared on 3 Nov 2011
Answered: francesco on 9 Nov 2013
I have up to 6 data pairs stored in a cell array.
f={x1 y1 x2 y2 x3 y3 x4 y4 x5 y5 x6 y6}
However, it many not always be all 6 data pairs, and I might end up with:
f={[] [] x2 y2 [] [] [] [] x5 y5 [] []}
It was shown to me that by using:
h=plot(f{~cellfun(@isempty,f)},'o','MarkerSize',1.5)
That empty cells are ignored. The data is plotted fine, but the linespec properties are not being applied to all data, only the last data series plotted.
Additionally,trying to change the marker edge and face color results in only the last handle being modified.
set(h(1),'MarkerEdgeColor','r','MarkerFaceColor','r')
set(h(2),'MarkerEdgeColor','y','MarkerFaceColor','y')
What am I missing?
Also, one issue that seems important, using this method, will there always be 6 handles, even if some are "blank" because their associated cells are empty? Is it possible to know that x3 y3 will always be f(3)?
  1 Comment
Jared
Jared on 3 Nov 2011
Actually, after more messing around, when plotting:
f={x1 y1 [] [] x3 y3 [] [] [] [] [] []};
x1 y1 is plotted as a yellow line, x 3 y3 is plotted as magenta 'o'. If h=plot(), setting h(1), and h(2) has no effect.

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Accepted Answer

Jan
Jan on 3 Nov 2011
If you use:
f{~cellfun(@isempty, f)}
The empty cells are not ignore, but they are not forwarded to PLOT at all. PLOT has no information, that there have been empty cells before.
Instead of removing the empty cells, you could insert Inf values. They are considered by PLOT, but do not produce a visible line.
BTW. cellfun('isempty', C) is much faster than cellfun(@isempty, C).
  1 Comment
Jared
Jared on 3 Nov 2011
Thanks for the tip on putting in Inf. I insert Inf into the cell array to "hold" the place where the data would be if the user desired it to be plotted. This allows me to be sure x6 y6 will always be assiciated with f(6), even if there is x1-5 and y1-5 are "empty." I guess this isn't a huge deal, other that ensuring data 6 is alway the same color, and knowing the f(6) should always be labeled as data 6 in the legend.

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More Answers (2)

Patrick Kalita
Patrick Kalita on 3 Nov 2011
I would suggest using a property-value pair to set the marker instead of a linespec string in this case:
f = { 1:3, rand(1,3), [], [], 4:6, rand(1,3), [], [], 7:9, rand(1,3), [], [] }
P = plot(f{:}, 'Marker','o','MarkerSize',1.5)
Also, you don't have to filter out the empty arrays. plot will only draw lines for non-empty arrays and return handles for the lines it drew:
>> P
P =
177.0447
178.0382
179.0382
The first element of P will be the handle of the line drawn with the first pair of x and y vectors.
  2 Comments
Patrick Kalita
Patrick Kalita on 3 Nov 2011
It seems like trying to do this one call to PLOT is making your life harder rather than easier. Have you considered multiple calls to PLOT combined with the HOLD command?

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francesco
francesco on 9 Nov 2013
right

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