Description Usage Arguments Details Value Author(s) See Also Examples

Construct the contrast matrix corresponding to specified contrasts of a set of parameters.

1 |

`...` |
expressions, or character strings which can be parsed to expressions, specifying contrasts |

`contrasts` |
character vector specifying contrasts |

`levels` |
character vector or factor giving the names of the parameters of which contrasts are desired, or a design matrix or other object with the parameter names as column names. |

This function expresses contrasts between a set of parameters as a numeric matrix.
The parameters are usually the coefficients from a linear model fit, so the matrix specifies which comparisons between the coefficients are to be extracted from the fit.
The output from this function is usually used as input to `contrasts.fit`

.
The contrasts can be specified either as expressions using `...`

or as a character vector through `contrasts`

.
(Trying to specify contrasts both ways will cause an error.)

The parameter names must be syntactically valid variable names in R and so, for example, must begin with a letter rather than a numeral.
See `make.names`

for a complete specification of what is a valid name.

Matrix which columns corresponding to contrasts.

Gordon Smyth

An overview of linear model functions in limma is given by the help page 06.LinearModels.

1 2 3 4 | ```
makeContrasts(B-A,C-B,C-A,levels=c("A","B","C"))
makeContrasts(contrasts="A-(B+C)/2",levels=c("A","B","C"))
x <- c("B-A","C-B","C-A")
makeContrasts(contrasts=x,levels=c("A","B","C"))
``` |

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