# ARTS built-in documentation server

## Workspace Method covmat_sxAddBlock

### Description

Add a block to the a priori covariance matrix covmat_sx
This functions adds a given matrix as a block in the covariance
matrix covmat_sx. The position of the block can be given by the generic
arguments ``i`` and ``j``, which should give the index of the retrieval quantity in
jacobian_quantities, which is given just by the order the quantities have been
added to the retrieval.
If arguments ``i`` and ``j`` are omitted, the block will be added as diagonal block
for the last added retrieval quantity.
If provided, the index ``i`` must be less than or equal to ``j``. Also the provided
block must be consistent with the corresponding retrieval quantities.

**Authors: **Simon Pfreundschuh

### Synopsis

### Variables

OUT+IN | covmat_sx | (CovarianceMatrix) | Covariance matrix of a priori distribution This covariance matrix describes the Gaussian a priori distribution for an OEM retrieval. |

IN | jacobian_quantities | (ArrayOfRetrievalQuantity) | The retrieval quantities in the Jacobian matrix. |

GIN | block | (Matrix, Sparse) | The block to add to the covariance matrix |

GIN | i | (Index, Default: -1) | Index of a retrieval quantity. Must satisfy ``i`` <= ``j``. |

GIN | j | (Index, Default: -1) | Index of a retrieval quantity. Must satisfy ``i`` <= ``j``. |