Many Welch tests | R Documentation |

Many Welch tests.

```
welch.tests(y, x, logged = FALSE, parallel = FALSE)
```

`y` |
The dependent variable, a numerical vector. |

`x` |
A matrix with the indendent variables. They must be integer valued data starting from 1, not 0 and be consecutive numbers. Instead of a data.frame with factor variables, the user must use a matrix with integers. |

`logged` |
Should the p-values be returned (FALSE) or their logarithm (TRUE)? |

`parallel` |
If you want to run the function in parallel set this equal to TRUE. |

For each categorical predictor variable, a Welch test is performed. This is useful in feature selection algorithms, to determine for which variable, the means of the dependent variable differ across the different values.

A two-column matrix with the test statistics (F test statistic) and their associated p-values (or their logarithm).

Michail Tsagris.

R implementation and documentation: Michail Tsagris mtsagris@uoc.gr.

B.L. Welch (1951). On the comparison of several mean values: an alternative approach. Biometrika, 38(3/4), 330-336.

` sp.logiregs, pc.sel `

```
y <- rnorm(200)
x <- matrix(rbinom(200 * 50, 2, 0.5), ncol = 50) + 1
a <- welch.tests(y, x)
```

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