matlabcontrol-charts

# Plot control at one figure and two subplots using built-in matlab functions

I try to plot control chart plot, and add to grid to every plot. But if I try to plot charts: for examples `xbar` and `r` charts, using `controlchart()` I get only last second plot (`r` chart), with grid.

My trouble: how to plot two plots and one figure non separatly, for example, two subplots?

My code for plotting control charts:

Example Data: (for every rows calculate mean and r data for CCharts plot)

`````` 102.8339   99.8529  101.0326  101.1049  101.8252 ;

98.7412   99.9311  101.5525  101.7223  102.3790;

101.8622  100.1905  102.1006  103.5855   99.9418;

101.3188   98.0557  102.5442  100.3331  100.5314;

99.6923  102.4384  101.0859  101.1873  100.7275;

...
``````

Code:

``````
%% Parameters for the initial normal distribution
mu = 101;
sigma = 1;

%% Number of data points
n = 100; % Total number of data points
%% Sample size for each point on the control chart
sample_size = 5;

%% Generate the first 25-30 points with a normal distribution
initial_points = randn(25 + randi(6, 1), sample_size) * sigma + mu;

%% Generate the control chart data
flag = randi(3, 1);
if flag == 1
mu_new = mu + randi([-1, 1]) * randi([1, 2]) * 0.15; % Randomly update mu
after_points = randn(74 + randi(6, 1), sample_size) * sigma + mu_new;
elseif flag == 2
sigma_new = sigma + randi([2, 3]) * 0.05; % Randomly update sigma
after_points = randn(74 + randi(6, 1), sample_size) * sigma_new + mu;
else
after_points = randn(74 + randi(6, 1), sample_size) * sigma + mu;
end

data  = [initial_points; after_points];

%% Create figure and plot
figure(1)

% Subplot 1 for the first control chart ('u' chart)
st1 = controlchart(data, 'charttype', 'xbar');
grid on;
grid minor;
title('Control Chart - Type xbar');

figure(2)
% Subplot 2 for the second control chart ('p' chart)
st2 = controlchart(data, 'charttype', {'r'});
grid on;
grid minor;
title('Control Chart - Type r');
``````

And I want to plot two CCharts with grids, and code not work:

``````% Create figure
figure;

% Subplot 1 for the first control chart ('xbar' chart)
subplot(2, 1, 1);
st1 = controlchart(data, 'charttype', {'xbar'});
grid on;
grid minor;

% Subplot 2 for the second control chart ('r' chart)
subplot(2, 1, 2);
st2 = controlchart(data, 'charttype', {'r'});
grid on;
grid minor;
``````

This code also not work:

``````st1 = controlchart(data, 'charttype', {'xbar','r'});
grid on;
grid minor;
``````

Solution

• The `parent` parameter can be used to send the plots to subplot axes. From the `controlchart` documentation:

parent — The handle of the axes to receive the control chart plot. Default is to create axes in a new figure. Not permitted if there are multiple chart types.

``````% Create figure
figure;

% Subplot 1 for the first control chart ('xbar' chart)
subplot(2, 1, 1);
st1 = controlchart(data, 'charttype', {'xbar'},'parent',gca);
grid on;
grid minor;

% Subplot 2 for the second control chart ('r' chart)
subplot(2, 1, 2);
st2 = controlchart(data, 'charttype', {'r'},'parent',gca);
grid on;
grid minor;
``````

2x1 subplot

Since the legends are the same, you could use `tiledlayout` to place a single legend for the figure.

``````%Create figure
tl = tiledlayout(2,1);

% Subplot 1 for the first control chart ('xbar' chart)
ax1 = nexttile;
st1 = controlchart(data, 'charttype', {'xbar'},'parent',ax1);
grid on;
grid minor;

% Subplot 2 for the second control chart ('r' chart)
ax2 = nexttile;
st2 = controlchart(data, 'charttype', {'r'},'parent',ax2);
grid on;
grid minor;

% Make single legend at top
delete(ax1.Legend)
ax2.Legend.Orientation = 'horizontal';
ax2.Legend.Layout.Tile = 'north';
``````

2x1 tiledlayout