Documentation 
Convert multivariate normal regression model to seemingly unrelated regression (SUR) model
DesignSUR = convert2sur(Design, Group)
Design  A matrix or a cell array that depends on the number of data series NUMSERIES.

Group  Contains information about how data series are to be grouped, with separate parameters for each group. Specify groups either by series or by groups:

DesignSUR = convert2sur(Design, Group) converts a multivariate normal regression model into a seemingly unrelated regression model with a specified grouping of the data series. DesignSUR is either a matrix or a cell array that depends on the value of NUMSERIES:
If NUMSERIES = 1, DesignSUR = Design, which is a NUMSAMPLESbyNUMPARAMS matrix.
If NUMSERIES > 1 and NUMGROUPS groups are to be formed, Design is a cell array with NUMSAMPLES cells, where each cell contains a NUMSERIESby(NUMGROUPS * NUMPARAMS) matrix of known values.
The original collection of parameters that are common to all series are replicated to form collections of parameters for each group.