plot f, f', f'' from csv with python & matplotlib

class rawDataObj:
       
        pointCount = 0
       
        colCount = 0
        columns = []       
        colLabels = []
       
        title = ""
       
# ===========================================

class Series:   

        def __init__(self):
               
                self.x = []
                self.y = []
       
        #~ def __init__(self, xIn, yIn):
               
                #~ if (len(xIn) != len(yIn)):
                        #~ raise lengthInequalityError, "length inequality"
                       
                #~ for zidx in range(len(xIn)):
                       
                        #~ self.x.append(xIn[zidx])
                        #~ self.y.append(yIn[zidx])
                       
        # ================================
       
        def DbyDX(self, xIn, yIn):
       
                if (len(xIn) != len(yIn)):
                       
                        raise setSizeInequalityError, 'set size inequality'       

                else:       
                       
                        for zidx in range(len(xIn) - 1):       
                               
                                xVal = (xIn[zidx + 1] + xIn[zidx]) / 2.0       
                                self.x.append(xVal)
                               
                                yVal = (yIn[zidx + 1] - yIn[zidx]) / (xIn[zidx + 1] - xIn[zidx])
                                self.y.append(yVal)
       
# ===========================================

import re

def loadrawDataObjFromFile(filePathAndName="/home/david/Desktop/ptpdrh.csv", hasHeader=False):
       
        try:
                f = open(filePathAndName, 'r')
               
                one = []
                two = []
               
                eof = False
               
                retDataObj = rawDataObj()
               
                lineNum = 0
                headerLineCount = 2
               
                while (eof == False):
                       
                        line = f.readline()
                        eof = (line == "")
                       
                        if (line != ""):
                               
                                lineNum = lineNum + 1
                               
                                elements = re.split(',', line)
                               
                                # strip newline (\n escape sequence) from last field of line
                                elements[len(elements) - 1] = elements[len(elements) - 1].rstrip("\n")
                               
                                # validate column count
                                if (lineNum > headerLineCount):
                                        if (len(elements) != retDataObj.colCount):
                                                raise inconsistentColumnCountError, ('column count inconsistent at data line ' + (retDataOb.pointCount + 1))
                               
                                if (lineNum <= headerLineCount):                   
                                                                               
                                        if (lineNum == 1):
                                               
                                                retDataObj.title = line
                                               
                                        elif (lineNum == 2):
                                       
                                                retDataObj.colCount = len(elements)               
                                       
                                                for num in range(retDataObj.colCount):                       
                                                        retDataObj.columns.append([])
                                               
                                                for label in elements:                                       
                                                        retDataObj.colLabels.append(label)
                               
                                else: # if (lineNum > headerLineCount)
                                       
                                        string = ""
                                       
                                        for zidx in range(retDataObj.colCount):                                       
                                               
                                                string = elements[zidx]
                                               
                                                if (len(string) == 0):
                                                        retDataObj.columns[zidx].append(None)                                               
                                                else:
                                                        retDataObj.columns[zidx].append(float(string))
                                               
                                        retDataObj.pointCount = retDataObj.pointCount + 1
                                               
                f.close()
               
        except IOError:
                print "io exception while attempting to load raw data"
                print "from file:"
                print filePathAndName
               
               
        return retDataObj
       
# ===========================================

# ===========================================

from pylab import *

filePath = "/home/david/Desktop/FinData/"
fileName = "RSA_CPI_1981-2008.csv"
filePathAndName = filePath + fileName

dataObj = loadrawDataObjFromFile(filePathAndName, True)

#for y in range(dataObj.colCount - 1):   
#    plot(dataObj.columns[0], dataObj.columns[y + 1], label=str(dataObj.colLabels[y + 1]))

fig = figure()
fig.canvas.set_window_title(dataObj.title)

# BASE SERIES
axBase = subplot(311)
baseLabel = label=str(dataObj.colLabels[dataObj.colCount - 1])
plot(dataObj.columns[0], dataObj.columns[dataObj.colCount - 1], label="base")
legend(numpoints=1, loc="upper left")

# FIRST DERIVATIVE
d1 = Series()
d1.DbyDX(dataObj.columns[0], dataObj.columns[dataObj.colCount - 1])
axD1 = subplot(312, sharex=axBase)
plot(d1.x, d1.y, label="d/dt")
legend(numpoints=1, loc="upper left")

 #SECOND DERIVATIVE
d2 = Series()
d2.DbyDX(d1.x, d1.y)
axD2 = subplot(313, sharex=axBase)
plot(d2.x, d2.y, label="d2/dt2")
legend(numpoints=1, loc="upper left")

#xlabel(dataObj.colLabels[0])

show()