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

Compute Row sums across columns of a numeric matrix-like object for each level of a grouping variable.

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`M` |
a matrix, data frame or vector of numeric data. Missing values are allowed. A numeric vector will be treated as a column vector. |

`group` |
a vector or factor giving the grouping, with one element per row of M. Default: rownames of M. |

`reord` |
if TRUE, then the result will be in order of sort(unique(group)), if FALSE (the default), it will be in the order that groups were encountered. |

`na_rm` |
logical (TRUE or FALSE). Should NA (including NaN) values be discarded? |

`big` |
is your object big and integer overflow is likely? If TRUE, then M is multiplied by 1.0 to ensure values are of type double (perhaps taking more RAM). |

`...` |
other arguments to be passed to or from methods. |

This function is a wrapper for base function `rowsum`

and is its "column" version.

A matrix-like object containing the sums by group. There will be one row per unique value of group.

Albert Dorador

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