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[programming] add box on string type

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Jan Grewe 2020-12-20 13:43:21 +01:00
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programming/lecture/programming.tex
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@ -176,11 +176,12 @@ As mentioned above, the data type associated with a variable defines how the sto
part. part.
\item \enterm{logical}: Boolean values that can be evaluated to \item \enterm{logical}: Boolean values that can be evaluated to
\code{true} or \code{false}. \code{true} or \code{false}.
\item \enterm{character}: ASCII characters. \item \enterm{character}: Unicode characters.
\item \enterm{string}: Strings of unicode characters, i.e. text.
\end{itemize} \end{itemize}
There is a variety of numeric data types that require different There is a variety of numeric data types that require different
amounts of memory and have different ranges of values that can be amounts of memory and have different ranges of values that can be
represented (table~\ref{dtypestab}). represented (table~\ref{dtypestab}). There are also more advanced data types which will not be used in this chapter but see box~\ref{box:advanced_dtypes} and box about strings \ref{box:strings}.
\begin{table}[t] \begin{table}[t]
\centering \centering
@ -1156,7 +1157,7 @@ segment of data of a certain time span (the stimulus was on,
\end{itemize} \end{itemize}
\end{exercise} \end{exercise}
\begin{ibox}[ht]{\label{advancedtypesbox}Advanced data types} \begin{ibox}[!ht]{\label{advancedtypesbox}Advanced data types}
Thoughout this script and the exercises we will limit ourselves to Thoughout this script and the exercises we will limit ourselves to
the basic data types introduced above (int, double, char, scalars, the basic data types introduced above (int, double, char, scalars,
vectors, matrices and strings). There are, however, \matlab{}- vectors, matrices and strings). There are, however, \matlab{}-
@ -1212,6 +1213,50 @@ ans =
\end{ibox} \end{ibox}
\begin{ibox}[!ht]{\label{box:string_dtype}The \enterm[string]{string} data type}
With release 2017a \matlab{} introduced the string data type which offers more convenience for handling text. A string scalar is created using double quotes: \varcode{s = "Hello world!";}.
The string object \varcode{s} now offers several methods to work on the stored information. Some of the most commonly used methods are listed below. Refer to the documentation for complete descriptions.
\begin{enumerate}
\item \varcode{append} -- appends another string to the string and returns the new string. As with the other functions the original is not affected.\vspace{-0.5em}
\item \varcode{contains} -- searches the string for the occurence of a another string, which is passed as an argument. Returns a logical that is true if the pattern was found.\vspace{-0.5em}
\item \varcode{split} -- splits the string into substrings. By default a blank is used as delimiter. You can pass any other string as an argument to spilt the string at each occurence of the passed pattern. Returns a vector of substrings.\vspace{-0.5em}
\item \varcode{join} -- The opposite of spilt. \varcode{join} takes a vector of strings and concatenates them to a single string. By default a blank is used as delimiter.\vspace{-0.5em}
\item \varcode{lower} -- returns a version of the string in which all characters are lower case. This is particularly useful when one compares user input or string arguments in a function in an case insensitive way.\vspace{-0.5em}
\item \varcode{upper} -- as above but all characters are converted to upper case.
\end{enumerate}
\paragraph{Example:}
A dataset is recorded on a specific recording date using an experimental subject and applying certain stimulus conditions. The recorded data should be stored in a file that contains this information separated by undersores.
\begin{lstlisting}[basicstyle=\ttfamily\scriptsize, caption={Using \varcode{join} to combine strings.}, label=usingjoin]
date = "2020-12-24";
subject = "subjectA";
condition = "control";
file_extension = ".dat";
filename = join([date, subject, condition], "_");
filename = filename.append(file_extension)
disp(filename)
ans =
"2020-12-24_subjectA_control.dat"
\end{lstlisting}
When reading the dataset during the analysis, we may want to extract the stimulus condtion or the subject name.
\begin{lstlisting}[basicstyle=\ttfamily\scriptsize, caption={Using \varcode{split} to cut a string at a delimiter.}, label=usingsplit]
disp(filename)
ans =
"2020-12-24_subjectA_control.dat"
filename = filename.erase(".dat"); % remove file extension
string_parts = filename.split("_"); % split at the underscore
% string_parts is a vector of the substrings
date = string_parts(1);
subject = string_parts(2);
condition = string_parts(3);
\end{lstlisting}
\end{ibox}
\section{Control flow}\label{controlstructsec} \section{Control flow}\label{controlstructsec}
Generally, a program is executed line by line from top to Generally, a program is executed line by line from top to