  Gravitational Waves (GWs) from the early universe and unresolved
astrophysical sources are expected to create a stochastic GW background (SGWB).
The GW radiometer algorithm is well suited to probe such a background using
data from ground based laser interferometric detectors. Radiometer analysis can
be performed in different bases, e.g., isotropic, pixel or spherical harmonic.
Each of these analyses possesses a common temporal symmetry which we exploit
here to fold the whole dataset for every detector pair, typically a few hundred
to a thousand days of data, to only one sidereal day, without any compromise in
precision. We develop the algebra and a software pipeline needed to fold data,
accounting for the effect of overlapping windows and non-stationary noise. We
implement this on LIGO's fifth science run data and validate it by performing a
standard anisotropic SGWB search on both folded and unfolded data. Folded data
not only leads to orders of magnitude reduction in computation cost, but it
results in a conveniently small data volume of few gigabytes, making it
possible to perform an actual analysis on a personal computer, as well as easy
movement of data. A few important analyses, yet unaccomplished due to
computational limitations, will now become feasible. Folded data, being
independent of the radiometer basis, will also be useful in reducing processing
redundancies in multiple searches and provide a common ground for mutual
consistency checks. Most importantly, folded data will allow vast amount of
experimentation with existing searches and provide substantial help in
developing new strategies to find unknown sources.
