First, generating arrays and matrices
1, Linspace (start,end,number), generates number between start and end number
>>> x = Linspace (0)>>>01 23456789.])
2, Logspace (start,end,number) produces numbers, between 10**start,10**end, the equivalent of an exponential function, the x-axis is divided into number of numbers, to calculate the exponent.
Same as 10**linspace (start,end,number) effect
3, Arange (l,u, s)
4,Meshgrid ()
>>> x = Arange (5)>>> y = arange (3)>>> x, y =Meshgrid (x, y)>>>Xarray ([[0,1,2,3,4],[0,1,2,3,4],[0,1,2,3,4]])>>>Yarray ([[0,0,0,0,0],[1,1,1,1,1],[2,2,2,2,2]])
5, Ix_ (a,b) Irregular selection of elements, where a, a can be a list or a tuple
>>> x = Reshape (Arange (25.0),(5,5))>>>Xarray ([[0.,1.,2.,3.,4.],[ 5.,6.,7.,8.,9.],[ Ten., One., A., -., -.],[ the., -., -., -., +.],[ -., +., A., at., -.]])>>> X[ix_ ([2,3],[0,1,2])] # Rows2&3, cols0,1and2Array ([[Ten., One., A.],[ the., -., -.]])>>> x[2:4,:3] # Same, Standard Slicearray ([[Ten., One., A.],[ the., -., -.]])>>> X[ix_ ([0,3],[0,1,4])] # No Slice equiv
Second, approximate
1,around, round
x=NP. Random. Randn (3)
X
Np. Around (x)
Np. Around (x,2) #近似精度为2位小数
[0.23073931 1.08865135-0.95564268][0. 1.-1.] [0.23 1.09-0.96]
2, floor (x), Ceil (x),
III. Statistical characteristics
1/sum, calculation and
A=np.reshape (Np.arange (Ten),(2,5));p rint A,'\ n'print Np.sum (a),'\ n'Print Np.sum (A,0),'\ n'Print Np.sum (A,1)[[0 1 2 3 4] [5 6 7 8 9]] $ [ 5 7 9 One -] [Ten *]
2/prod the same characteristics as SUM, he is the product of the calculation
A=np.reshape (Np.arange (1,5),(2,2));p rint A,'\ n'? Print Np.prod (a),'\ n'Print Np.prod (A,0),'\ n'Print Np.prod (A,1),'\ n'[[1 2] [3 4]] - [3 8] [ 2 A]
3,exp,log--equivalent to ln (),log10,sqrt,Square,absolute, ABS, Sign is the manipulation of elements
A=NP.RANDOM.RANDN (2,3);p rint A,'\ n'print Np.abs (a) print np.sign (a)
[[-0.35632202-0.56913468-0.5054189 ] [-0.13182024 1.62914028 1.57704769]] [[ 0.35632202 0.56913468 0.5054189 ] [ 0.13182024 1.62914028 1.57704769]][[-1. -1. -1.] [-1.1.1.]]
4, for the operation of complex numbers, the following operations are also the operation of the elements
- Real (a) or a.real, the real part of the plural
- Imag (A) or a.imag, imaginary part of a complex number
- Conj (A) , conjugate, conjugate plural
5,Unique (A) is the operation of all elements, equivalent to the Python set (), the effect of the redo
6, in1d (A, B)
>>> x = arange (10.0)>>> y = arange (5.0,15.0) >>> in1d (x, y) array ([False, False, False, False, False, True, True, True, true, True], Dtype =
bool)
7,union1d (A, B), returns the unique set of elements in 2 arrays. Equivalent set merge
8,intersect1d (A, B) is equivalent to the collection of the pickup
9,setdiff1d (b), in set A, not in set B
10,setxor1d (A, B), equivalent to take a set XOR, only in a set of elements
11. Sort
A=NP.RANDOM.RANDN (2,3);p rint aprint Np.sort (A,1) Print Np.sort (A,0) Print Np.sort (A,none) [[2.33262004-2.17579511 1.02508041] [-0.11651321 1.02673882 1.25183328]][[-2.17579511 1.02508041 2.33262004] [-0.11651321 1.02673882 1.25183328]][[-0.11651321-2.17579511 1.02508041] [ 2.33262004 1.02673882 1.25183328]][-2.17579511-0.11651321 1.02508041 1.02673882 1.25183328 2.33262004]
Note: The difference between a.sort () and sort (a), one will change the data structure, one will not.
>>> x = Randn (3)>>>Xarray ([2.70362768, -0.80380223, -0.10376901])>>>sort (x) array ([-0.80380223, -0.10376901,2.70362768])>>>Xarray ([2.70362768, -0.80380223, -0.10376901])>>> X.sort () # in-Place , changes x>>>Xarray ([-0.80380223, -0.10376901,2.70362768])
12,Max, amax, argmax , min, Amin , Argmin
Max is the method of the array, Amax is the function, Argtmax returns
A=NP.RANDOM.RANDN (3,5);p rint aprint Np.amax (A,1) Print Np.amax (A,0) Print Np.amax (A,none) [[-1.20363617e-01 6.09840964e-01-2.42821192e-01-1.87136859e+00-9.24036132e-01] [ -2.12137767e-04-4.49847000e-01 6.05104140e-02 5.00253683e-01 1.63359279e+00] [ -3.41458128e-01-9.52592527e-01 8.66845911e-01-1.26919405e+00 1.67080515e+00]][ 0.60984096 1.63359279 1.67080515][ -2.12137767e-04 6.09840964e-01 8.66845911e-01 5.00253683e-01 1.67080515e+00]1.67080515388
13,minimum (a , b), maximum (A, B) compares two arrays, returns the smallest or largest number in the corresponding position of two arrays
Introduction to Python for statistics,analysis Note 3