I'd like to give my graph background color based on a string value

Hello,

I have a table, out of which I extracted three arrays: time, AvePressure and markers. I'd like to plot AvePressure over time, and i want to give the graph different background colors based on the value of markers (some are strings while others are empty. In total, there are 10 types of markers).

Thanks in advance!

Answer 1

[DGM]

Here's one way using basic colormapping and an image object as an underlay.

% fake data
x = linspace(0,1,100);
y = [x.^2; x.^1.5; x];
classes = [repmat({'a'},[1 25]),repmat({[]},[1 5]), ...
    repmat({'b'},[1 25]),repmat({[]},[1 10]), ...
    repmat({'c'},[1 25]),repmat({[]},[1 10])];

% define the mapping
classnames = {'a','b','c'};
classcolor = jet(numel(classnames)); % or any other color table
classcolor = [1 1 1; classcolor]; % one extra color is needed for the empty case

% find the classes and create color stripe
mask = cellfun(@isnumeric,classes); % "empty" might mean either [] or '' or ""
classes(mask) = {''}; % but in order to compare against strings/char, it can't be []
[~,idx] = ismember(classes,classnames); % create index array
bgpict = ind2rgb(uint8(idx),classcolor); % convert to an image stripe

% plot things
plot(x,y); hold on % plot the things
extents = [xlim; ylim]; % store the calculated axes extents

% draw the image underlay
hi = image(extents(1,:),extents(2,:),bgpict,'alphadata',0.2);
uistack(hi,'bottom') % move to background
xlim(extents(1,:)) % restore previous extents
ylim(extents(2,:))

Answer 2

[Mandar]

I understand you want to change the background colour of the graph. Refer the link below to know more about changing the background colour of the graph.

Link: https://in.mathworks.com/matlabcentral/answers/166737-how-do-i-make-a-plot-background-black

Answer 3

[Image Analyst]

See this demo that let's you change virtually anything about the graph:

% Demo to make a black graph with red Y axis, green X axis, and yellow grid.  Markers are magenta with green lines between them.
% Initialization steps:
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clearvars;
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 24;
% Create sample data.
X = 1 : 20;
Y = rand(1, 20);
% Plot green lines between the markers.
plot(X, Y, 'g-', 'LineWidth', 3);
hold on;
% Plot magenta markers.
plot(X, Y, 'ms', 'LineWidth', 3, 'MarkerSize', 15);
grid on;
title('Y vs. X, Font Size 20', 'FontSize', 20, 'Color', 'b', 'FontWeight', 'bold');
% Make labels for the two axes.
xlabel('X Axis, Font Size 18');
ylabel('Y axis, Font Size 24');
yticks(0 : 0.2 : 1);
% Get handle to current axes.
ax = gca
% Now let's have fun changing all kinds of things!
% This sets background color to black.
ax.Color = 'k'
ax.YColor = 'r';
% Make the x axis dark green.
darkGreen = [0, 0.6, 0];
ax.XColor = darkGreen;
% Make the grid color yellow.
ax.GridColor = 'y';
ax.GridAlpha = 0.9; % Set's transparency of the grid.
% Set x and y font sizes.
ax.XAxis.FontSize = 18;
ax.YAxis.FontSize = 24;
% Make the axes tick marks and bounding box be really thick.
ax.LineWidth = 3;
% Let's have the tick marks go outside the graph instead of poking inwards
ax.TickDir = 'out';
% The below would set everything: title, x axis, y axis, and tick mark label font sizes.
% ax.FontSize = 34;
% Bold all labels.
ax.FontWeight = 'bold';
hold off
% Now do stuff with the figure, as opposed to the axes control that is ON the figure.
% Maximize the figure
g = gcf; % Get handle to the current figure.
g.WindowState = 'maximized'; % Make it full screen.
g.Name = 'Demo by Image Analyst'; % Put a custom string into the titlebar.
g.NumberTitle = 'off'; % Don't have it put "Figure 1" before the name.
g.MenuBar = 'figure'; % or 'none'
g.ToolBar = 'figure'; % or 'none'