0 
import numpy as np
def readMatrix(filename):
    rows = []
    for line in open(filename):
        columns = []
        for number in string.split(line):
            columns.append(float(number))
        rows.append(columns)
    return numpy.array(rows)

def writeMatrix(a, filename):
    f = open(filename, 'w')
    for row in a:
        for number in row:
            f.write(str(number) + ' ')
        f.write('\n')
    f.close()

def TaylorMatrixExp(A):
    I = identity(len(A))
    return (I + A + (1./2.)*(dot(A,A)) + (1./6.)*(dot(dot(A,A),A)) + (1./24.)*(dot(dot(A,A),dot(A,A))))

A = readMatrix('matrix.txt')

l, v = eig(A)

L = identity(len(l))

for i in xrange(len(l)):
    L[i][i] = array(exp(l))[i]

VLV = dot(dot(v,L),inv(v))

writeMatrix(VLV,'expA.txt')

ExponentA = TaylorMatrixExp(A)
writeMatrix(ExponentA,'expA.txt')

它读取的矩阵是：
2 2
16 6

我定义了两个 3 函数，readMatrix（从文本文件中读取矩阵）、writeMatrix（将矩阵写入文件）和 TaylorMatrixExp（获取数组并展开它）。我最初使用 readMatrix 读取包含上述矩阵的文本文件并将其放入数组 A。我将 A 的特征值放入数组 l 以及 A 的特征向量并将其放入数组 v。我最终将值放入数组 l 穿过单位矩阵的对角线。然后我调用 writeMatrix 函数并将指数写入“expA.txt”，然后再次调用 writeMatrix 函数并将矩阵 ExponentA 写入“expA.txt”。但是，它替换了原始矩阵，我不希望它这样做。

and I want it to write to a file
some# some#
some# some#

some#2 some#2
some#2 some#2

but instead it replaces the first matrix
some#2 some#2
some#2 some#2

4

1 回答 1

4 
f = open(filename, 'a')

Lets you append to the file rather than rewrite it, which is what you're currently doing with the 'w' argument, which is why that matrix is replaced.

于 2012-12-04T20:13:11.073 回答