when i give a 3X3 matrix as input,it returns index error at line: m[0][0]*m[1][1]-m[0][1]*m[1][0]
import copy
def matrixdeterminant(m):
if len(m)==1:
return m[0]
elif len(m)==2:
return m[0][0]*m[1][1]-m[0][1]*m[1][0]
else:
matrixdeterminantlist=copy.deepcopy(m)
determinantlist=[]
m.pop(0)
for i in range(len(matrixdeterminantlist[0])):
for j in range(len(m)):
m[j].pop(i)
determinantlist.append(matrixdeterminantlist[0][i]*matrixdeterminant(m)*(-1)**(i+2))
m=copy.deepcopy(matrixdeterminantlist)
return sum(determinantlist)
First issue I can spot: you wrote return m[0] rather than return m[0][0] for the case where len(m) == 1.
If m is a 1x1 matrix, then m looks something like [[x]], and you want to return x, not [x], so you have to return m[0][0], not m[0].
Another important issue in your code is the way you pop elements from m and then try to restore m from its copies. This is overly complicated and you restore m wrongly inside the loop, so at some points the dimensions of m are all screwed-up. I recommend to avoid using .pop at all, and instead, build the submatrices using list comprehensions.
Here is a simplified version:
def matrixdeterminant(m):
if len(m)==1:
return m[0][0]
elif len(m)==2:
return m[0][0]*m[1][1]-m[0][1]*m[1][0]
else:
determinantlist=[]
sign = 1
for i in range(len(m)):
submatrix = [row[1:] for j,row in enumerate(m) if j != i]
minor = matrixdeterminant(submatrix)
determinantlist.append(sign * m[i][0] * minor)
sign *= -1
return sum(determinantlist)
And here is yet another version:
from itertools import cycle
def matdet(m):
if len(m) == 1:
return m[0][0]
else:
return sum(
s * mj[0] * matdet([row[1:] for i,row in enumerate(m) if i != j])
for s,(j,mj) in zip(cycle([1,-1]), enumerate(m))
)
Once it's producing numerical values instead of error messages, I strongly encourage you to test your determinant function by comparing its output on big random matrices, against the output of a matrix determinant function from a standard python module such as numpy or sympy or scipy: