kate88 - 8 months ago 72

Python Question

I created the histogram below:

and was wondering if instead of plotting the whole graph (in blue) I could just plot the top edge (in black)?

or just fit the line to match the top of the distribution?

my code is:

`plt.hist(histogramData, bins=200, normed=True, cumulative=True, edgecolor='b', facecolor='None')`

I tried removing 'edgecolor' and 'facecolor' but it does not seem to work...

Thank for your help!

Answer

I think pylabs histogram codes uses numpys `np.histogram()`

function, yielding bins and counts; so if you use that together wit the standard `plot()`

command, you are done (just remember to also do the `np.cumsum()`

on the counts of the `np.histogram()`

for the cummulative look).

Edit:
Regarding the comment, I quote from the `numpy.histogram()`

documentation:

Returns:

hist: arrayThe values of the histogram. See normed and weights for a description of the possible semantics.

bin edges: array of dtype floatReturn the bin edges (length(hist)+1).

Thus, to plot your data in the desired way:

```
hist, bins = np.histogram(data, bins=200)
plt.plot( bins[:-1], np.cumsum(hist) )
```

or if you want to be more precise, you could even put the data values in the bin center:

```
offset = bins[1:]-bins[:-1]
plt.plot( bins[:-1]+offset, np.cumsum(hist) )
```