skew
Syntax
skew(X, [biased=true])
Parameters
X is a vector/matrix.
biased (optional) is a Boolean value indicating whether the result is biased. The default value is true, meaning the bias is not corrected.
Details
Return the skewness of X. The calculation skips null values.
The calculation uses the following formulas in different cases:
When biased=true:
When biased=false:
If X is a matrix, calculate the skewness of each column of X and return a vector.
If X is a table, calculate the skewness of each column of X and return a table.
The skew function also supports querying partitioned tables and
distributed tables with bias correction.
Note:
Both DolphinDB and SciPy calculate skewness in their
skew functions using the Fisher-Pearson coefficient, but they
differ in several respects. DolphinDB ignores NULL values during computation, while
SciPy allows you control this behavior explicitly through the nan_policy
parameter. SciPy also provides the keepdims parameter, which preserves the
original array dimensions after computation.Examples
Please note that as the example below uses a random number generator, the result is slightly different each time it is executed.
x=norm(0, 1, 1000000);
skew(x);
// output: -0.00124
x[0]=100;
skew(x);
// output: 0.983656
m=matrix(1..10, 1 2 3 4 5 6 7 8 9 100);
m;| #0 | #1 |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 4 |
| 5 | 5 |
| 6 | 6 |
| 7 | 7 |
| 8 | 8 |
| 9 | 9 |
| 10 | 100 |
skew(m);
// output: [0,2.630083823883674]