This module has several functions for creating and manipulating
histograms (binned data). Use require("histogram") to load it.
Compute a 1-d histogram
h = hist1d ([h,] pnts, grid [, &rev])
The hist1d function bins a set of points pnts into a
1-d histogram using bin-edges given by the grid argument. The
optional last argument &rev is a reference to a variable
whose value will be assigned the reverse-indices of the histogram.
The first argument h is optional. If present and non-NULL, it
will be used as the histogram buffer with new binned values added to
it. That is, the following statements are equivalent:
h = h + hist1d (pnts, grid);
h = hist1d (h, pnts, grid);
The value of the ith bin in the histogram is given by the number of
values in the pnts array that satisfy
grid[i]<=X<grid[i+1] where X represents the value of
the candidate point. The last bin of the histogram represents an
overflow bin with the right bin edge at plus infinity. The grid is
required to be sorted into ascending order.
The reverse-indices array is an array-of-arrays of indices such that
rev[i] is an array of indices into the pnts array that
have fallen into the ith bin.
hist1d_rebin, hist2d, hist2d_rebin, hist_bsearch
Compute a 2-d histogram
h = hist2d ([h,] xpnts, ypnts, xgrid, ygrid [, &rev])
The hist2d function bins a set of (x,y) pairs
represented by the xpnts and ypnts arrays into a 2-d
histogram using bin-edges given by the xgrid and ygrid
arguments. The optional last argument &rev is a reference to
a variable whose value will be assigned the reverse-indices of the
histogram. The first argument is also optional and, if present and
non-NULL, will be used for the histogram values.
The value of the bin [i,j] of the histogram is given by the
number of (X,Y) pairs that satisfy xgrid[i]<=X<xgrid[i+1] and
ygrid[j]<=Y<ygrid[j+1]. The bins at the extreme edges of the
histogram represent overflow bins with the upper bin edge at plus
infinity. The grids are required to be sorted into ascending order.
The reverse-indices array is a 2-d array-of-arrays of indices such that
rev[i,j] is an array of indices into the xpnts and
ypnts arrays that have fallen into the bin [i,j].
hist1d, whist2d, hist2d_rebin, hist1d_rebin, hist_bsearch
Rebin a 1-d histogram
new_h = hist1d_rebin (new_grid, old_grid, old_h)
The hist1d_rebin function rebins a histogram old_h
with bin edges defined by old_grid into a histogram with bin
edges given by new_grid. The rebinning operation preserves
the normalization of the histogram where the grids overlap.
Unlike the hist1d function which returns an integer array,
the hist1d_rebin function returns an array of doubles since
the new grid does not have to be commensurate with the old grid.
hist1d, hist2d_rebin, hist2d, hist_bsearch
Rebin a 2-d histogram
new_h = hist2d_rebin (new_xgrid, new_ygrid, old_xgrid, old_ygrid, old_h)
The hist2d_rebin function rebins a 2-d histogram old_h
with bin edges defined by old_xgrid and old_ygrid into
a 2-d histogram with bin edges given by new_xgrid and
new_ygrid.
Unlike the hist2d function which returns an integer array,
the hist2d_rebin function returns an array of doubles since
the new grids do not have to be commensurate with the old grids.
hist1d_rebin, hist2d, whist2d, hist_bsearch
Perform a binary search
i = hist_bsearch (x, xbins)
The hist_bsearch function performs a binary search for the
bin i satisfying xbins[i]<=x<xbins[i+1]. If the value
x is greater than or equal to the value of the last bin, the
index of the last bin will be returned. If x is smaller than
the value of the first bin (xbins[0]), then the function will
return the index of the first bin, i.e., 0. The grid is
required to be sorted into ascending order.
If the value of x is an array, an array of indices will be
returned.
As pointed out above, if the value of x is less than the value
of the first bin, the index of the first bin will be returned even
though x does not belong to the bin. If this behavior is not
desired, then such points should be filtered out before the binary
search is performed.
hist1d, hist1d_rebin
Created a weighted 1-d histogram
h = whist1d (pnts, wghts, grid [,&rev [,&weight_func]]
The whist1d function creates a 1-dimensional weighted
histogram. The value of the ith bin in the histogram is given by a
function applied to values of the wghts that correspond to
those values in the pnts array that satisfy
grid[i]<=X<grid[i+1] where X represents the value of
the candidate point. The last bin of the histogram represents an
overflow bin with the right bin edge at plus infinity. The grid is
required to be sorted into ascending order.
If the optional fourth argument &rev is present, upon return
it will be set to the array of reverse-indices of the histogram. The
optional &weight_func argument may be used to specify the
function to be applied to the weights array. By default, the
sum function will be used.
The source code to this function may be found in histogram.sl.
As such, it is available only after this file has been loaded.
Simply importing the module will not load this function into the
interpreter.
hist1d, whist2d, hist1d_rebin
Created a weighted 2-d histogram
h = whist2d (xpnts, ypnts, wghts, xgrid, ygrid [,&rev [,&weight_func]]
The whist2d function creates a 2-dimensional weighted
histogram. The value of the bin [i,j] of the histogram is
given by a function applied to those values in the wghts array
that correspond to the (X,Y) pairs that satisfy
xgrid[i]<=X<xgrid[i+1] and ygrid[i]<=Y<ygrid[i+1]. The
bins at the extreme edges of the histogram represent overflow bins
with the upper bin edge at plus infinity. The grids are required to
be sorted into ascending order.
If the optional sixth argument &rev is present, upon return
it will be set to the array of reverse-indices of the histogram. The
optional &weight_func argument may be used to specify the
function to be applied to the weights array. By default, the
sum function will be used.
The source code to this function may be found in histogram.sl.
As such, it is available only after this file has been loaded.
Simply importing the module will not load this function into the
interpreter.
hist2d, whist1d, hist1d, hist2d_rebin