MATLAB Fundamentals>Specialized Data Types>Representing Discrete Categories>(1/6) Introduction
Representing Discrete Categories
When text labels are intended to represent a finite set of possibilities, a string array may use more memory than a categorical array. There are functions designed to work with categories of data, so if your text describes a group or category, this is often the best data type.
当文本标签旨在表示一组有限的可能性时，字符串数组可能比分类数组使用更多的内存。有些函数是为处理数据类别而设计的，因此，如果您的文本描述了一个组或类别，这通常是最好的数据类型。
MATLAB Fundamentals>Specialized Data Types>Representing Discrete Categories>(2/6) Converting to and Operating on Categoricals
This code sets up the activity.
x = ["C","B","C","A","B","A","C"]
This line of code would produce an error.
% histogram(x)说明1：You can convert a string array to a categorical using the categorical function.
任务1：Convert x into a categorical array named y.
解答：
y = categorical(x)说明2：Categorical arrays take up less memory than cell arrays of strings.
任务2：Issue the whos x y command to see how much memory each variable uses.
解答：
whos x y任务3：
You can see the categories represented in a categorical array using the categories function on the categorical array.
解答：
cats = categories(y)任务4：
Create a variable named iC which contains values of true corresponding to the values in y that equal C.
解答：
iC = y == "C"任务5：
Create a variable named iNB which contains values of true corresponding to the values in y that are not equal to B.
解答：
iNB = y ~= "B"附加练习：Try indexing into y with iC and iNB.
解答：
iCidx = y(iC)
iNBidx = y(iNB)笔记：
（1）a string array may use more memory than a categorical array字符串数组比分类数组占用更多内存；
（2）任务4和5后面部分可以不使用括号，执行运算顺序为从又向左，即先计算“等于”或“不等于”逻辑，在将结果赋值给左边变量。
