MATLAB Function Reference

histogram2

Compute a two dimensional histogram

Syntax

```[result,descriptor] = histogram2(x,y)
[result,descriptor] = histogram2(x,y,descriptor)
```

Description

The `discriptor` describes the cells of the histogram. The `discriptor` consists of two row vectors with three elements `[lowerx,upperx,ncellx;lowery,uppery,ncelly]`. The default values are `lowerx=min(x)-deltax/2`, `upperx=max(x)+deltax/2` and `ncellx=ceil(length(x)^(1/3))`, where `deltax=(max(x)-min(x))/(length(x)-1)` and similar for `y`.

Its assumed that `lowerx < upperx`, ```lowery < uppery```, `ncelly >= 1`, `ncelly >= 1` and `length(x) == length(y)`. Futhermore its assumed that both `x` and `y` are row vectors.

The `result` is a matrix vector containing the histogram of `x` and `y`. The indices `(indexx,indexy)` of the histogram cells are computed by ```indexx = round( (x(i)-lowerx) / (upperx-lowerx) * ncellx ) + 1/2``` and ```indexy = round( (x(i)-lowery) / (uppery-lowery) * ncelly ) + 1/2```. If one of the indices is out of the range ```1 <= indexx <= ncellx``` or ```1 <= indexy <= ncelly```, consequently `x(i) < lowerx`, `upperx <= x(i)`,`y(i) < lowery` or `uppery <= y(i)`, the elements `x(i)` and `y(i)` are excluded from the histogram.