A.set(branch[0],j+1,1)
A.set(branch[1],j+1,-1)
#set source branch
A.set(1,numBranches,-1)
A.set(numNodes,numBranches,1)
f=open(output,'w')
f.write(str(numBranches)+'\n')
#number of nodes (subtract one taken as ground)
f.write(str(numNodes-1)+'\n')
#print J,R,E for each branch (0,1,0)
for i in range(1,numBranches):
f.write('0,1,0\n')
#print source branch
f.write('0,1,1\n') #1V source, 1ohm R_test
#print incidence matrix
for i in range(1,A.rows): #stop at rows, and not rows+1 as we discard last node taken as ground
f.write(str(int(A.get(i,1))))
for j in range(2,A.columns+1):
f.write(','+str(int(A.get(i,j))))
f.write('\n')
f.close()
