Why do some people grow wisdom teeth while others do not? What is the probability that they grow? Why do I grow wisdom teeth! ! !
Classification of missing data
- Missing completely at random
- Missing at random
- Not missing at random
to understand why before handling missing data will be missing data
1. power off the machine, resulting in a measured value has lost
2. Measure did not happen, such as columns: Some data is not investigated in the course of the investigation, or is invalid
in In R, NA stands for missing value (unavailable), it may be 0, it may be any value
. Add na.rm=TRUE to the function to skip the missing value and calculate it, and reduce the number of missing values to calculate the total.
Use is.na(x) to check whether the vector contains missing values. If there are missing values, the corresponding position shows TRUE to
remove the missing values in the data. Use na.omit(x)
other missing data.
Missing data NaN represents an impossible value
lnf Represents infinity, which is divided into positive infinity and negative infinity. It represents the
difference between infinity and infinitesimal missing values.
NA is an existing value, but I don’t know how many
NaN does not exist.
Inf exists, is infinity or infinitesimal, but it means impossible value.
Use is.nan(x) to identify the non-existent value, is.infinite(x) to identify the corresponding value, and return TRUE or FALSE