2020-12-14 Nominal Data 名义数据
Nominal Data
The term “nominal” comes from Latin and can be translated as “being so in name only”. The only information carried by nominal data is the group an observation belongs to. An example of this could be color. You could encode yellow as 1 and blue as 2, but these numbers would have no specific value nor meaning. And such an encoding would not automatically make green equal to 1.5.
When it comes to mathematical operations, there ain’t much you can do here. One can only compute the mode (the most frequent value) of a nominal variable. Other measures, such as the mean or the median, make no sense.
名义数据
“名义”这个词来自于拉丁语，可以解释为“仅仅名称如此”。名义数据唯一带的信息是数据归属的群组。举一例子比如颜色。你可以定义黄色是1、蓝色是2，但是这些数字没有特殊的含义或意义。这样的转化不能自动让绿色等于1.5。
当在数学计算中，我们无能为力。我们只能计算名义数据的众数（最频繁出现的数字）。其他计算方法都没有意义，比如平均值或者中位数。
