How to return empty vector of figures

Question

Erwin Werkhoven 2022-7-4

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1752935-how-to-return-empty-vector-of-figures

回答： Steven Lord 2022-7-4

Hi all,

I have a function draw_plots with an input vector plot_configs that should return a vector of figures. If the plot_configs vector is empty it should return an empty figure vector. But with the code underneath I get this error:

Output argument "figures" (and possibly others) not assigned a value in the execution with "draw_plots" function.

That makes perfect sense. So I tried to initialize figures with figures = Figure.empty but that doesn't work either:

Unable to resolve the name 'Figure.empty'.

So how to initialize/return an empty vector of figures? Thanks in advance!

Please note that we're not interested in showing the figures, just saving them to disk.

function figures = draw_plots(plot_configs, tsc, masks, n_rows, n_cols)

plot_configs = plot_configs([plot_configs.enable]); % filter enabled plot configs

color_order = [

0.0 0.0 0.8;

0.0 0.5 0.0;

0.8 0.0 0.0;

0.0 0.8 0.8;

0.8 0.0 0.8;

0.8 0.8 0.0;

0.2 0.2 0.2];

n_plots = length(plot_configs);

n_plots_per_page = n_rows * n_cols;

% figures = Figure.empty; <-- How I hoped to fix the error

for pc_idx = 1:n_plots

plot_idx = mod(pc_idx, n_plots_per_page);

if (plot_idx == 0) % Fill up figure with subplots until max number of plots per page

plot_idx = n_plots_per_page;

elseif (plot_idx == 1)

fig = figure('defaultAxesColorOrder', color_order, 'visible', 'off');

inner_w = 1200;

inner_h = 400 * n_rows;

fig.InnerPosition(3) = inner_w;

fig.InnerPosition(4) = inner_h;

fig_idx = ceil(pc_idx / n_plots_per_page);

figures(fig_idx) = fig;

end

sub = subplot(n_rows, n_cols, plot_idx);

hold on;

box on;

grid on;

pc = plot_configs(pc_idx);

mask = masks.get(pc.filter);

data_x = pc.signal_x.getter(tsc);

data_x = data_x(mask);

if (strcmp(pc.signal_x.generic_name, 'Time'))

data_x = datetime(data_x, 'ConvertFrom', 'datenum', 'Format', 'yyyy-MM-dd HH:mm:ss');

end

for signal_y = pc.signals_y

data_y = signal_y.getter(tsc);

data_y = data_y(mask);

plot = scatter(sub, data_x, data_y, 1, 'filled');

fontsize(plot, 8, "pixels")

end

title_str = pc.title;

xlabel_str = pc.signal_x.generic_name + ' [' + pc.unit_x + ']';

ylabel_str = pc.unit_y;

title(title_str, 'Interpreter', 'none');

xlabel(xlabel_str, 'Interpreter', 'none');

ylabel(ylabel_str, 'Interpreter', 'none');

end

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Bruno Luong 2022-7-4

在 MATLAB Online 中打开

MATLAB figure class is

matlab.ui.Figure

Bruno Luong 2022-7-4

编辑：Bruno Luong 2022-7-4

在 MATLAB Online 中打开

You might even do this:

%if n_plots == 0
figures = []; % instead of figures = Figure.empty
%    return
%end

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Answer 1

Rik 2022-7-4

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1752935-how-to-return-empty-vector-of-figures#answer_999495

在 MATLAB Online 中打开

plot_configs=[];

figures = draw_plots(plot_configs)

figures =

1×0 empty Figure array.

plot_configs=ones(1,2);

figures = draw_plots(plot_configs)

figures =

1×2 Figure array: Figure Figure

function figures = draw_plots(plot_configs, varargin)

n_plots=numel(plot_configs);

if n_plots==0

figures=figure('visible', 'off');

close(figures)

figures(1)=[];

return

end

for n=1:n_plots

fig = figure(varargin{:}, 'visible', 'off');

figures(n) = fig;

end

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Erwin Werkhoven 2022-7-4

Bruno Luong's suggestion is simpler than this one and seems to work too. Thanks for thinking along though!

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Answer 2

Steven Lord 2022-7-4

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1752935-how-to-return-empty-vector-of-figures#answer_999770

在 MATLAB Online 中打开

Preallocate the array using gobjects.

F = gobjects(1, 3)

F =

1×3 GraphicsPlaceholder array: GraphicsPlaceholder GraphicsPlaceholder GraphicsPlaceholder

F(2) = figure;

F

F =

1×3 graphics array: GraphicsPlaceholder Figure GraphicsPlaceholder

To check if an element has been filled in, ask if it is a matlab.ui.Figure.

isa(F(3), 'matlab.ui.Figure') % false
ans = logical
   0
isa(F(2), 'matlab.ui.Figure') % true
ans = logical
   1

Or if they've all been filled in you can ask if the array as a whole is a matlab.ui.Figure.

F(3) = figure;

F(1) = figure;

F

F =

1×3 Figure array: Figure Figure Figure

isa(F, 'matlab.ui.Figure')

ans = logical

1

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