对NumPy矩阵有问题吗

Question

我非常熟悉MATLAB，但是我在学习Python时遇到了困难。你知道吗

问题是创建一个数组X（idx，：），在该数组中，我用读取的每一行递增idx，并将X（idx，：）赋给一行数据。下面是数据和一个Python示例程序。你知道吗

文件：“示例数据”

TRE-G3T- Triumph-        0.000 10/01/2013 227001.30 1760.00000 10/01/2013 227016.30   41 31 27.35998  -70 40 19.00843      -28.130        0.707   882922.244  2652775.212      -65.517      -24.677      -13.470        0.020        0.022        0.041        0.051      -13.469       -0.771   0.0109 2   1.80  7        0.005 S              0.032    -0.024     0.001  -0.256  -0.162   0.554
TRE-G3T- Triumph-        0.000 10/01/2013 227001.40 1760.00000 10/01/2013 227016.40   41 31 27.35993  -70 40 19.00854      -28.123        0.714   882922.235  2652775.207      -65.519      -24.679      -13.464        0.020        0.022        0.041        0.051      -13.463       -0.650   0.0136 2   1.80  7        0.006 S              0.005    -0.039     0.057   0.066   0.301  -0.602
TRE-G3T- Triumph-        0.000 10/01/2013 227001.50 1760.00000 10/01/2013 227016.50   41 31 27.35997  -70 40 19.00848      -28.128        0.710   882922.240  2652775.211      -65.518      -24.678      -13.468        0.020        0.022        0.041        0.051      -13.467       -0.631   0.0103 2   1.80  7        0.007 S              0.012    -0.011    -0.005   0.006  -0.094   0.606
TRE-G3T- Triumph-        0.000 10/01/2013 227001.60 1760.00000 10/01/2013 227016.60   41 31 27.36002  -70 40 19.00858      -28.122        0.715   882922.232  2652775.216      -65.520      -24.676      -13.462        0.020        0.022        0.041        0.051      -13.462       -0.829   0.0109 2   1.80  7        0.007 S              0.014    -0.021     0.056  -0.021   0.214  -0.435
TRE-G3T- Triumph-        0.000 10/01/2013 227001.70 1760.00000 10/01/2013 227016.70   41 31 27.36005  -70 40 19.00849      -28.125        0.712   882922.239  2652775.219      -65.518      -24.675      -13.465        0.020        0.022        0.041        0.051      -13.465       -1.040   0.0106 2   1.80  7        0.006 S              0.011     0.000     0.011   0.110   0.264  -0.284

Python程序：

#!/usr/local/bin/python 


import numpy as np
import matplotlib.pyplot as plt


def dms2deg(deg,min,sec):
# jad - 20131103
        sgn = float(deg) / abs(float(deg))
        return sgn * (abs(float(deg)) + (float(min) + (float(sec)/60) ) / 60 )


def decdeg2dms(dd):
# http://stackoverflow.com/questions/2579535/how-to-convert-dd-to-dms-in-python
   is_positive = dd >= 0
   dd = abs(dd)
   minutes,seconds = divmod(dd*3600,60)
   degrees,minutes = divmod(minutes,60)
   degrees = degrees if is_positive else -degrees
   return (degrees,minutes,seconds)





#  indices into GrafNav output record
idx0 =  7   #  index of GPS seconds
idx1 =  8   #  beginning index for lat / lon
idx2 = 28   #  solution quality

f = open('sample_data','r')


ctr2 = -1

X=[]
X=np.array(X)



for line in f:

    var = line.split()
    l=len(var)

    if l > 35:                 #  data has more than 35 columns
        GPS_sec = var[idx0]

        lat_deg = var[idx1+0]
        lat_min = var[idx1+1]
        lat_sec = var[idx1+2]

        lon_deg = var[idx1+3]
        lon_min = var[idx1+4]
        lon_sec = var[idx1+5]

        h_ell = var[idx1+6]

        latd = dms2deg(lat_deg,lat_min,lat_sec)
        lond = dms2deg(lon_deg,lon_min,lon_sec)


        Q = var[idx2]
        stdev = var[idx2-4]
        h_sep = var[idx2-2]
        amb_drift = var[idx2-1]
        nsat = var[idx2+2]

        ctr2 += 1
             X=np.array([float(GPS_sec),float(latd),float(lond),float(h_ell),int(Q),int(nsat),float(stdev),float(h_sep),float(amb_drift)])
        print GPS_sec,  latd,  lond, h_ell,  Q, nsat, stdev, h_sep, amb_drift

f.close()

Answer 1

如果你能把问题集中在你真正想问的问题上，你会得到更好的答案。你的代码中有很多与问题无关的东西，但很难挖掘到真正的内容。我想你想要这样的东西：

X = []
for line in f:
    ....
    row = np.array([GPS_sec, latd, lond, h_ell, Q, nsat, stdev, h_sep, amb_drift],
                   dtype=float)
    X.append(row)

X = np.array(X)

这样做的目的是将最终数组的行保存在一个列表中，然后在循环之后将其转换为一个数组。另外，您应该知道ndarrays只能有一个数据类型，我相信这和matlab是一样的，所以不清楚您试图通过执行np.array([float(a), int(b)])来实现什么。希望这有帮助。你知道吗

Answer 2

似乎您只是想将文本数据转换为numpyarray。正如@BiRico所指出的，在一个array中不能有多个数据类型dtype，如果必须这样做，就必须使用strutured array，或者更好的方法是使用pandas数据帧。你知道吗

而且numpy有构建IO函数genfromtxt()，速度非常快。使用它而不是硬代码1：

>>> dtypeLS=[('Var0', 'S10'),
    ('Var1', 'S10'),     
    ('Var2', 'f8'),      
    ('Var3', '<M8[D]'),  
    ('Var4', 'f8'),      
    ('Var5', 'f8'),      
    ('Var6', '<M8[D]'),  
    ('Var7', 'f8'),      
    ('Var8', 'f8'),      
    ('Var9', 'f8'),      
    ('Var10', 'f8'),     
    ('Var11', 'f8'),     
    ('Var12', 'f8'),     
    ('Var13', 'f8'),     
    ('Var14', 'f8'),     
    ('Var15', 'f8'),     
    ('Var16', 'f8'),     
    ('Var17', 'f8'),     
    ('Var18', 'f8'),     
    ('Var19', 'f8'),     
    ('Var20', 'f8'),     
    ('Var21', 'f8'),     
    ('Var22', 'f8'),     
    ('Var23', 'f8'),     
    ('Var24', 'f8'),     
    ('Var25', 'f8'),     
    ('Var26', 'f8'),     
    ('Var27', 'f8'),     
    ('Var28', 'f8'),     
    ('Var29', 'f8'),     
    ('Var30', 'f8'),     
    ('Var31', 'f8'),     
    ('Var32', 'S10'),    
    ('Var33', 'f8'),     
    ('Var34', 'f8'),     
    ('Var35', 'f8'),     
    ('Var36', 'f8'),     
    ('Var37', 'f8'),     
    ('Var38', 'f8')]
>>> a=genfromtxt('temp.txt', dtype=dtypeLS)
>>> a[0]
('TRE-G3T-', 'Triumph-', 0.0, datetime.date(2013, 10, 1), 227001.3, 1760.0, datetime.date(2013, 10, 1), 227016.3, 41.0, 31.0, 27.35998, -70.0, 40.0, 19.00843, -28.13, 0.707, 882922.244, 2652775.212, -65.517, -24.677, -13.47, 0.02, 0.022, 0.041, 0.051, -13.469, -0.771, 0.0109, 2.0, 1.8, 7.0, 0.005, 'S', 0.032, -0.024, 0.001, -0.256, -0.162, 0.554)
>>> a['Var11']
array([-70., -70., -70., -70., -70.])
>>> a['Var12']
array([ 40.,  40.,  40.,  40.,  40.])
>>> a['Var13']
array([ 19.00843,  19.00854,  19.00848,  19.00858,  19.00849])
>>> np.sign(a['Var11'])*(np.abs(a['Var11'])+a['Var12']/60+a['Var13']/3600)
array([-70.67194679, -70.67194682, -70.6719468 , -70.67194683, -70.6719468 ])     

最后，就像在Matlab中一样，如果您想让事情快速运行，请始终进行矢量化。请参阅最后一行中的dd到dms转换代码。你知道吗

另外，我必须将您的日格式从10-01-2013更改为2013-10-01，以使用datetimedtype。你知道吗