[scientific research data processing] [basic] category variable frequency analysis chart, numerical variable distribution chart and normality test (including lognormal)

1、 Category variables and numerical variables

First, variables can be divided into two categories ： Category variable （Category Variables） And numeric variables （Numeric variables）. The distinction between the two is not absolute , Relative transformation can be realized . For example, grades belong to numerical variables , However, if it is classified according to good, medium and poor , Will become a category variable ; Type of work variable belongs to category variable , However, when the number of categories is too large, it will be regarded as a numerical variable in the analysis , For example, there are many types of work in aircraft carriers , Different numbers correspond to different types of work .

1.1 The use of category variables and continuous variables in this paper

Definition ： Frequency analysis is for a single variable （ Category variable ） Analysis of , The results of the analysis are different categories （ Different value ranges ） Frequency of （frequency）, And the percentage corresponding to the frequency （percentage）/ Or cumulative percentage （cumulative percentages）, See the table below and the figure below （ Left ）.

If it's a continuous variable , Generally, it will be divided according to the value range to form category variables , For example, the accident occurrence time variable , It will be divided according to different time ranges , See the picture below （ Right ）.

Table source ：
Jingguoxun , Liumengxia .2015-2019 Statistics and law analysis of coal mine gas accidents in China in [J/OL]. Security