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Py之Numpy：Numpy库简介、安装、使用方法、案例应用之详细攻略
Py之Numpy：Numpy库中常用函数的简介、应用之详细攻略
Numpy库中常用函数的简介、应用
1、X, Y = np.meshgrid(X, Y)
| meshgrid Found at: numpy.lib.function_base Return coordinate matrices from coordinate vectors. Make N-D coordinate arrays for vectorized evaluations of N-D scalar/vector fields over N-D grids, given one-dimensional coordinate arrays x1, x2,..., xn. .. versionchanged:: 1.9 1-D and 0-D cases are allowed. Parameters ---------- x1, x2,..., xn : array_like 1-D arrays representing the coordinates of a grid. indexing : {'xy', 'ij'}, optional Cartesian ('xy', default) or matrix ('ij') indexing of output. See Notes for more details. .. versionadded:: 1.7.0 sparse : bool, optional If True a sparse grid is returned in order to conserve memory. Default is False. .. versionadded:: 1.7.0 copy : bool, optional. If False, a view into the original arrays are returned in order to conserve memory. Default is True. Please note that ``sparse=False, copy=False`` will likely return noncontiguous arrays. Furthermore, more than one element of a broadcast array may refer to a single memory location. If you need to write to the arrays, make copies first. .. versionadded:: 1.7.0 Returns ------- X1, X2,..., XN : ndarray For vectors `x1`, `x2`,..., 'xn' with lengths ``Ni=len(xi)`` , return ``(N1, N2, N3,...Nn)`` shaped arrays if indexing='ij' or ``(N2, N1, N3,...Nn)`` shaped arrays if indexing='xy' with the elements of `xi` repeated to fill the matrix along the first dimension for `x1`, the second for `x2` and so on. Notes ----- This function supports both indexing conventions through the indexing keyword argument. Giving the string 'ij' returns a meshgrid with matrix indexing, while 'xy' returns a meshgrid with Cartesian indexing. In the 2-D case with inputs of length M and N, the outputs are of shape (N, M) for 'xy' indexing and (M, N) for 'ij' indexing. In the 3-D case with inputs of length M, N and P, outputs are of shape (N, M, P) for 'xy' indexing and (M, N, P) for 'ij' indexing. The difference is illustrated by the following code snippet:: xv, yv = np.meshgrid(x, y, sparse=False, indexing='ij') for i in range(nx): for j in range(ny): # treat xv[i,j], yv[i,j] xv, yv = np.meshgrid(x, y, sparse=False, indexing='xy') for i in range(nx): for j in range(ny): # treat xv[j,i], yv[j,i] In the 1-D and 0-D case, the indexing and sparse keywords have no effect. See Also -------- index_tricks.mgrid : Construct a multi-dimensional "meshgrid" using indexing notation. index_tricks.ogrid : Construct an open multi-dimensional "meshgrid" using indexing notation. |
从坐标向量返回坐标矩阵。 建立N-D坐标阵列，在N-D网格上对N-D标量/向量场进行向量化计算，给定一维坐标阵列x1, x2，…,xn。 . .versionchanged:: 1.9 允许1-D和0-D。 参数 ---------- x1, x2,…， xn: array_like 表示网格坐标的一维数组。 索引:{'xy'， 'ij'}，可选 Cartesian ('xy'，默认)或矩阵('ij')索引的输出。 参见注释了解更多细节。 . .versionadded: 1.7.0 稀疏:bool，可选 如果为真，则返回一个稀疏网格以保存内存。默认是假的。 . .versionadded: 1.7.0 复制:bool，可选。如果为假，则返回原始数组的视图 为了保存记忆。默认是正确的。请注意，' ' sparse=False, copy=False ' '将可能返回不相邻的数组。此外，广播数组中的多个元素可以引用单个内存位置。如果需要对数组进行写入，请首先进行复制。 . .versionadded: 1.7.0 返回 ------- X1, X2,…XN: ndarray 对于向量“x1”，“x2”，…， 'xn'加上length ' ' ' Ni=len(xi) ' '， 返回' ' (N1, N2, N3，…Nn) ' '形数组如果索引='ij'或' ' (N2, N1, N3，…Nn) ' '形数组如果索引='xy'与元素' xi '重复填充矩阵沿第一个维度为' x1 '，第二个为' x2 '，以此类推。 笔记 ----- 这个函数通过索引关键字参数支持两种索引约定。给出字符串'ij'返回一个带矩阵索引的meshgrid，而'xy'返回一个带笛卡尔索引的meshgrid。 在输入长度为M和N的二维情况下，输出的形状为(N, M)，表示“xy”索引，(M, N)表示“ij”索引。在输入长度为M、N和P的3-D情况下，输出的形状(N、M、P)表示“xy”索引，(M、N、P)表示“ij”索引。区别如下面的代码片段所示:: xv yv = np。meshgrid(x, y, sparse=False, index ='ij') i在range(nx)内: j in range(ny): 治疗xv[i,j]， yv[i,j] xv yv = np。meshgrid(x, y, sparse=False, index ='xy') i在range(nx)内: j in range(ny): 在1-D和0-D情况下，索引和稀疏关键字没有影响。。 另请参阅 -------- index_tricks。mgrid:使用索引符号构造一个多维“meshgrid”。 index_tricks。ogrid:使用索引符号构造一个开放的多维“meshgrid”。 |
| Examples -------- >>> nx, ny = (3, 2) >>> x = np.linspace(0, 1, nx) >>> y = np.linspace(0, 1, ny) >>> xv, yv = np.meshgrid(x, y) >>> xv array([[ 0. , 0.5, 1. ], [ 0. , 0.5, 1. ]]) >>> yv array([[ 0., 0., 0.], [ 1., 1., 1.]]) >>> xv, yv = np.meshgrid(x, y, sparse=True) # make sparse output arrays >>> xv array([[ 0. , 0.5, 1. ]]) >>> yv array([[ 0.], [ 1.]]) `meshgrid` is very useful to evaluate functions on a grid. >>> x = np.arange(-5, 5, 0.1) >>> y = np.arange(-5, 5, 0.1) >>> xx, yy = np.meshgrid(x, y, sparse=True) >>> z = np.sin(xx**2 + yy**2) / (xx**2 + yy**2) >>> h = plt.contourf(x,y,z) |
