Set figure size after creating image

fig = plt.gcf() #Gets the current figure
fig.set_size_inches(10,10, forward=True) # changes size of figure. Forward must equal True to make the change

Python Subplots (some with different sizes)

http://matplotlib.org/users/tight_layout_guide.html

Plotting netCDF data in Python

http://www.hydro.washington.edu/~jhamman/hydro-logic/blog/2013/10/12/plot-netcdf-data/

Symbols in labels

To put a symbol or label, such as a degree sign.

pl.xlabel('Temperature ($^{\circ}\!$ C)')

advances in computing will benefit weather forecasts

news about advances in computing abilities is always exciting news fore weather forecasters. Check out this article...

http://www.engadget.com/2014/08/07/ibm-synapse-supercomputing-chip-mimics-human-brain/?ncid=txtlnkusaolp00000618

Relative Maximun and MInimum

It's easy to find the max and min of an array, but sometimes you want to find all local max an mins.

From post here:

import numpy as np
from scipy.signal import argrelextrema

x = np.random.random(12)

# for local maxima
argrelextrema(x, np.greater)

# for local minima
argrelextrema(x, np.less)

Produces
>>> x
array([ 0.56660112,  0.76309473,  0.69597908,  0.38260156,  0.24346445,
    0.56021785,  0.24109326,  0.41884061,  0.35461957,  0.54398472,
    0.59572658,  0.92377974])
>>> argrelextrema(x, np.greater)
(array([1, 5, 7]),)
>>> argrelextrema(x, np.less)
(array([4, 6, 8]),)

Note, these are the indices of x that are local max/min. To get the values, try:
>>> x[argrelextrema(x, np.greater)[0]]

change tick mark size

http://matplotlib.org/api/axes_api.html#matplotlib.axes.Axes.tick_params
Example
# Create Figure
fig = plt.figure(1)
ax = fig.add_subplot(111)
#increase size of tick marks
ax.tick_params('both', length=20, width=2, which='major')
ax.tick_params('both', length=10, width=1, which='minor')

Python Accessing all the files in a directory

This is a handy link that gets file names from a directory:
http://stackoverflow.com/questions/18262293/python-open-every-file-in-a-folder

For example: 
path = 'C://Users/person/Pictures' for filename in glob.glob(os.path.join(path,'*.jpg')):

     print filename

results in:

C:\Users\Brian\Pictures\East.jpg
C:\Users\Brian\Pictures\North.jpg
C:\Users\Brian\Pictures\Rocketeer.jpg
C:\Users\Brian\Pictures\South.jpg
C:\Users\Brian\Pictures\WIN_20140711_105811_edited.jpg

etc.

Easy Legend

The easiest way to make a legend is to give the plot a label when you first make the plot.
Example:

plt.plot(times_utc,duchesne, label="Duchesne")
plt.plot(times_utc,mtn_home, label="Mountain Home")
plt.plot(times_utc,horsepool, label="Horsepool")

plt.legend(loc=2)

Managing DateTime Tick Marks

When creating plots, one issue I continue to face is managing the tick marks. Customizing DateTime ticks is especially difficult. But I think I've found the best way to manage this problem.

When making a plot with a DateTime array on the x-axis, use this:

#Import packages
import matplotlib.pyplot as plt
from matplotlib.dates import DateFormatter, YearLocator, MonthLocator, DayLocator, HourLocator

# Create the plot
ax = plt.subplot(1,1,1)
plt.(datetime_array, y_variable)

# Format Ticks
# Find months
months = MonthLocator()
# Find days
days = DayLocator()
# Find each 0 and 12 hours
hours = HourLocator(byhour=[0,12])
# Find all hours
hours_each = HourLocator()

# Tick label format style
dateFmt = DateFormatter('%d:%H')

# Set the x-axis major tick marks
ax.xaxis.set_major_locator(hours)
# Set the x-axis labels
ax.xaxis.set_major_formatter(dateFmt)
# For additional, unlabeled ticks, set x-axis minor axis
ax.xaxis.set_minor_locator(hours_each)

Example Result:
A major tick mark every 0 and 12 hour with the label formatted as [Day:Hour]. A minor tick mark on every hour.

Plotting Ceilometer data with imshow()

I have plotted a month of ceilometer data with matplotlib using imshow(). This figure shows backscatter at the mountain meteorology lab for January 2014.

Simple error catching

I always get stuck with errors when building scripts. Sometimes I want the program to do something even if there is an error. Here is an example of a simple way to catch errors:

try:
file = h5py.File(file.h5, 'r')
print 'Yes, this file exists'

except:
print 'Didn't work'
sys.exit()

Here I try to open the HDF5 file called 'file.h5'. If the file exists we print "Yes, this file exists."
If there is an error when the computer tries to open the file--for example, the file can not be found--then we print "Didn't work" and the python program closes.

Save matplotlib figures and save to a server

On my personal computer I have created many figures with matplotlib. I've always used  plt.show() to show the figures and plt.savefig() to save the images, but I've had a lot of trouble saving a figure onto the server. 
At work, python is installed on the server, but saving the figures has never worked. I always get the error no display name and no $DISPLAY environment variable
Turns out I was just missing a single line of code. After importing matplotlib type mpl.use('Agg'). This will fix the problem.

Example:

import matplotlib as mpl
mpl.use('Agg')   #Not sure why, but this makes saving to a server possible.
import matplotlib.pyplot as plt
import numpy as np

x = np.arange(0,50,.2)
y = np.sin(x)

plt.plot(x,y)
plt.title("This works!!! I'm so excited")
plt.savefig(path to save image + image_name.png)
plt.close()

Results in:

Downloads

Where can you download Python and Python packages???

Python is distributed through Enthought Canopy.

Packages can be downloaded through Surgeforce, the package website, and I also found this website that has a lot of packages in one place: http://www.lfd.uci.edu/~gohlke/pythonlibs/