[plotting] scatterplot

plotting/code/scatterplot.m

@@ -0,0 +1,28 @@
+x = 1:2:100;
+y = (0.5 .* x - 0.56) + randn(size(x)) .* 5.;
+
+f = figure();
+set(f, 'paperunits', 'centimeter', 'papersize', [15, 5], ...
+    'paperposition', [0, 0, 15, 5], 'color', 'white');
+
+subplot(1, 3, 1);
+scatter(x, y, 15, 'r', 'filled');
+xlabel('x');
+ylabel('y');
+text(-35, max(ylim) * 1.075,'A', 'FontSize', 12);
+
+subplot(1, 3, 2)
+scatter(x, y, 1:length(x), 'r');
+xlabel('x');
+ylabel('y');
+text(-35, max(ylim) * 1.075,'B', 'FontSize', 12);
+
+subplot(1, 3, 3)
+colors = zeros(length(x),3);
+colors(:,1) = round(1:255/length(x):255)/255';
+scatter(x, y, 15, colors, 'filled')
+xlabel('x');
+ylabel('y');
+text(-35, max(ylim) * 1.075,'C', 'FontSize', 12);
+
+saveas(f, '../lecture/images/scatterplot.png')

plotting/lecture/plotting-chapter.tex

@@ -16,10 +16,6 @@
 
 \input{plotting}
 
-\subsection{Scatter plot}
-
-\subsection{Histograms}
-
 \subsection{Heatmaps}
 
 \subsection{3-D plot}

plotting/lecture/plotting.tex

@@ -444,7 +444,51 @@ various examples and the respective code on their website
 
 For some types of plots we present examples in the following sections.
 
-\subsection{Line plot, subplots}
+\subsection{Scatter}
+
+For displaying events or pairs of x-y coordinates the standard line
+plot is not optimal. Rather, we use \code[scatter()]{scatter} for this
+purpose. For example, we have a number of measurements of a system's
+response to a certain stimulus intensity. There is no dependency
+between the data points, drawing them with a line-plot would be
+nonsensical (figure\,\ref{scatterplotfig}\,A).  In contrast to
+\codeterm{}{plot} we need to provide x- and y-coordinates in order to
+draw the data. In the example we also provide further arguments to set
+the size, color of the dots and specify that they are filled
+(listing\,\ref{scatterlisting1}).
+
+\lstinputlisting[caption={Creating a scatter plot with red filled dots.},
+  label=scatterlisting1, firstline=9, lastline=9]{scatterplot.m}
+
+We could have used plot for this purpose and set the marker to
+something and the line-style to ``none'' to draw an equivalent
+plot. Scatter, however offers some more advanced features that allows
+to add two more dimensions to the plot
+(figure\,\ref{scatterplotfig}\,B,\,C). For each dot one can define an
+individual size and color. In this example the size argument is simply
+a vector of the same size as the data that contains number from 1 to
+the length of 'x' (line 1 in listing\,\ref{scatterlisting2}). To
+manipulate the color we need to specify a length(x)-by-3 matrix. For
+each dot we provide an individual color (i.e. the RGB triplet in each
+row of the color matrix, lines 2-4 in listing\,\ref{scatterlisting2})
+
+
+\lstinputlisting[caption={Creating a scatter plot with size and color
+    variations. The RGB triplets define the respective color intensity
+    in a range 0:1. Here, we modify only the red color channel.},
+  label=scatterlisting2, linerange={15-15, 21-23}]{scatterplot.m}
+
+\begin{figure}[t]
+  \includegraphics{scatterplot}
+  \titlecaption{Scatterplots.}{Scatterplots are used to draw
+    datapoints where there is no direct dependency between the
+    individual measurements (like time). Scatter offers several
+    advantages over the standard plot command. One can vary the size
+    and/or the color of each dot.}\label{scatterplotfig}
+\end{figure}
+
+
+\subsection{Subplots}
 A very common scenario is to combine several plots in the same
 figure. To do this we create so-called subplots
 figures\,\ref{regularsubplotsfig},\,\ref{irregularsubplotsfig}. The