#+STARTUP: showall

#+TITLE:     Class 16: matplotlib 2 - graphing
#+AUTHOR:    Kurt Schwehr
#+EMAIL:     schwehr@ccom.unh.edu
#+DATE:      <2011-10-25 Tue>
#+DESCRIPTION: Marine Research Data Manipulation and Practices
#+KEYWORDS: ipython matplotlib
#+LANGUAGE:  en
#+OPTIONS:   H:3 num:nil toc:t \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t
#+OPTIONS:   TeX:t LaTeX:nil skip:t d:nil todo:t pri:nil tags:not-in-toc
#+INFOJS_OPT: view:nil toc:nil ltoc:t mouse:underline buttons:0 path:http://orgmode.org/org-info.js
#+LINK_HOME: http://vislab-ccom.unh.edu/~schwehr/Classes/2011/esci895-researchtools/

* Introduction

This is part 2 of the matplotlib introduction.  The material in classes 15 and 16 is
covered in a video:

http://youtu.be/zwzR0z0_Gn0

* Last time - lecture 15

We had this script last time to create the x,y offsets in meters of
the GPS

#+BEGIN_SRC python
#!/usr/bin/env python

import pyproj 
import numpy as np

def wander_list():
    geod = pyproj.Geod(ellps='WGS84')
    x,y,z,quality,satellites,hdop = np.loadtxt('2011-10-11.gga.dat.bz2', unpack=True)
    
    x_ave = np.average(x)
    y_ave = np.average(y)

    print x_ave,y_ave

print '__name__:', __name__
if __name__ == '__main__':
    wander_list()
#+END_SRC

We want to create a better script that can save the data out for
reuse.

* Matplotlib continued

#+BEGIN_SRC python
import wander
reload wander # You have to reload after the first import to get more changes
dir, m = wander.wander_list('2011-10-11.gga.dat.bz2')

cla()
plot dir
#+END_SRC

Errr... dir runs -180 to +180.  Let's make that 0..360:

#+BEGIN_SRC python
dir360 = [ d if d>0 else d+360 for d in dir ]
#+END_SRC

Didn't get that last line?  I'll explain it more in a video.

* Fancier plotting - histograms and subplots

It would be nice to be able to make a figure with multiple plots and
maybe have a histogram.  Let's try making a histogram first.

#+BEGIN_SRC python
cla()
hist(m)
hist(m, bins=30)
hist(m, bins=100)
#+END_SRC

Which is a reminder that you are warned that histograms are not a
stable concept.  How they look depends heavily on the number of bins.

*Warning:* matplotlib is designed to follow how matlab does plotting.  That
means that subplots start counting from 1, not 0.  Bummer.

#+BEGIN_SRC python
cla()
subplot (411)
plot(dir360)
plot(x)
subplot (412)
plot(y)
subplot (413)
plot(m)
subplot (414)
hist(m, bins=200)
#+END_SRC

* Working with arrays

We can start building up capabilities

#+BEGIN_SRC python
zeros(30)
ones(10)
concatonate( (zeros(100), ones(100), zeros(100) ) )
#+END_SRC


* TODO Questions

- What is "interactive mode" for matplotlib?
- Switching figures
- Splitting 15 into 15 & 16