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#! /usr/bin/env python
#-*- coding: utf-8 -*-
import random
from math import sqrt
from PIL import Image, ImageDraw
def readfile(filename):
lines=[line for line in file(filename)]
# First line is the column titles
colnames=lines[0].strip().split('\t')[1:]
rownames=[]
data=[]
for line in lines[1:]:
p=line.strip().split('\t')
# First column in each row is the rowname
rownames.append(p[0])
# The data for this row is the remainder of the row
data.append([float(x) for x in p[1:]])
return rownames,colnames,data
def pearson(v1,v2):
# Simple sums
sum1=sum(v1)
sum2=sum(v2)
# Sums of the squares
sum1Sq=sum([pow(v,2) for v in v1])
sum2Sq=sum([pow(v,2) for v in v2])
# Sum of the products
pSum=sum([v1[i]*v2[i] for i in range(len(v1))])
# Calculate r (Pearson score)
num=pSum-(sum1*sum2/len(v1))
den=sqrt((sum1Sq-pow(sum1,2)/len(v1))*(sum2Sq-pow(sum2,2)/len(v1)))
if den==0: return 0
return 1.0-num/den
def tanimoto(v1, v2):
c1, c2, shr = 0, 0, 0
for i in range(len(v1)):
if v1[i] != 0:
c1 += 1 # in v1
if v2[i] != 0:
c2 += 1 # in v2
if v1[i] != 0 and v2[i] != 0:
shr += 1 # in both
return 1.0 - (float(shr) / (c1 + c2 - shr))
def kcluster(rows,distance=pearson,k=4):
# Determine the minimum and maximum values for each point
ranges=[(min([row[i] for row in rows]),max([row[i] for row in rows]))
for i in range(len(rows[0]))]
# Create k randomly placed centroids
clusters=[[random.random()*(ranges[i][1]-ranges[i][0])+ranges[i][0]
for i in range(len(rows[0]))] for j in range(k)]
lastmatches=None
for t in range(100):
print 'Iteration %d' % t
bestmatches=[[] for i in range(k)]
# Find which centroid is the closest for each row
for j in range(len(rows)):
row=rows[j]
bestmatch=0
for i in range(k):
d=distance(clusters[i],row)
if d<distance(clusters[bestmatch],row): bestmatch=i
bestmatches[bestmatch].append(j)
# If the results are the same as last time, this is complete
if bestmatches==lastmatches: break
lastmatches=bestmatches
# Move the centroids to the average of their members
for i in range(k):
avgs=[0.0]*len(rows[0])
if len(bestmatches[i])>0:
for rowid in bestmatches[i]:
for m in range(len(rows[rowid])):
avgs[m]+=rows[rowid][m]
for j in range(len(avgs)):
avgs[j]/=len(bestmatches[i])
clusters[i]=avgs
return bestmatches
def scaledown(data,distance=pearson,rate=0.01):
n=len(data)
# The real distances between every pair of items
realdist=[[distance(data[i],data[j]) for j in range(n)]
for i in range(0,n)]
# Randomly initialize the starting points of the locations in 2D
loc=[[random.random(),random.random()] for i in range(n)]
fakedist=[[0.0 for j in range(n)] for i in range(n)]
lasterror=None
for m in range(0,1000):
# Find projected distances
for i in range(n):
for j in range(n):
fakedist[i][j]=sqrt(sum([pow(loc[i][x]-loc[j][x],2)
for x in range(len(loc[i]))]))
# Move points
grad=[[0.0,0.0] for i in range(n)]
totalerror=0
for k in range(n):
for j in range(n):
if j==k: continue
# The error is percent difference between the distances
errorterm=(fakedist[j][k]-realdist[j][k])/realdist[j][k]
# Each point needs to be moved away from or towards the other
# point in proportion to how much error it has
grad[k][0]+=((loc[k][0]-loc[j][0])/fakedist[j][k])*errorterm
grad[k][1]+=((loc[k][1]-loc[j][1])/fakedist[j][k])*errorterm
# Keep track of the total error
totalerror+=abs(errorterm)
# If the answer got worse by moving the points, we are done
if lasterror and lasterror<totalerror: break
lasterror=totalerror
# Move each of the points by the learning rate times the gradient
for k in range(n):
loc[k][0]-=rate*grad[k][0]
loc[k][1]-=rate*grad[k][1]
return loc
def draw2d(data,labels,jpeg='mds2d.jpg'):
img=Image.new('RGB',(2000,2000),(255,255,255))
draw=ImageDraw.Draw(img)
for i in range(len(data)):
x=(data[i][0]+0.5)*1000
y=(data[i][1]+0.5)*1000
draw.text((x,y),labels[i],(0,0,0))
img.save(jpeg,'JPEG')
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