Zero crossing with hysteresis

Find zero crossing of a vector or a matrix with hysteresis thresholds

Usage:
D = ZCwHyst(vec_in, hist_l, hist_h, figh)
Inputs:
vec_in - vector or a matrix of data. if vec_in is a matrix, the function
takes each column as an entry.
hist_l - lower hysteresis bound. should be 0 or below.
hist_h - upper hysteresis bound. should be 0 or above.
figh (optional) - figure handle for plot. To disable the plot, use
only 3 inputs or assign figh as []. To draw in a specific figure
window, assign the window number to figh. For a new figure window,
assign -1 to figh.

Output:
ZC = vector of the zero crossings.

In order to draw stairs graph of the crossings, use the following code:
ZC(ZC==0) = -1;
stairs(ZC)