任務(wù)7-1-4-數(shù)組形狀修改

ETL數(shù)據(jù)預(yù)處理技術(shù)主講人：王浩任務(wù)7-1-4數(shù)組形狀修改01.reshape02.03.目錄ravelNdarray.flattenCONTENTSnumpy.reshape(a,newshape,order=‘C’)：在不改變數(shù)據(jù)的情況下為數(shù)組賦予新的形狀>>>arr1=np.arange(8)>>>arr1array([0,1,2,3,4,5,6,7])>>>arr1.shape(8,)#將arr1變換為二維數(shù)組>>>arr2=np.reshape(arr1,(2,4))>>>arr2array([[0,1,2,3],[4,5,6,7]])##打印arr2形狀>>>arr2.shape(2,4)>>>arr3=np.reshape(arr1,(2,2,2))>>>arr3array([[[0,1],[2,3]],[[4,5],[6,7]]])##打印arr3形狀>>>arr3.shape(2,2,2)#將arr3轉(zhuǎn)換為一維數(shù)組>>>arr4=np.reshape(arr3,8)>>>arr4array([0,1,2,3,4,5,6,7])##打印arr4形狀>>>arr4.shape(8,)#重塑之后的數(shù)組形狀要與待重塑數(shù)組的形狀相容，否則報(bào)錯(cuò)>>>arr5=np.reshape(arr1,(3,3))ValueError:cannotreshapearrayofsize8intoshape(3,3)>>>arr1=np.arange(8)>>>arr1array([0,1,2,3,4,5,6,7])>>>arr2=np.reshape(arr1,(2,-1))>>>arr2array([[0,1,2,3],[4,5,6,7]])>>>arr1=np.arange(8)>>>arr1array([0,1,2,3,4,5,6,7])>>>arr2=np.reshape(arr1,(1,-1))>>>arr2array([[0,1,2,3,4,5,6,7]])>>>arr2.shape(1,8)>>>arr3=np.reshape(arr1,(-1,1))>>>arr3array([[0],[1],[2],[3],[4],[5],[6],[7]])>>>arr3.shape(8,1)>>>arr4=np.reshape(arr3,-1)>>>arr4array([0,1,2,3,4,5,6,7])>>>arr4.shape(8,)numpy.ravel(a,order=‘C’)：返回展平成一維的數(shù)組元素。一般返回的是數(shù)組視圖（view），需要的時(shí)候（例如order改變）才會(huì)返回?cái)?shù)組的副本（copy）a：數(shù)組order：{‘C’,’F’,‘A’,‘K’}，可選參數(shù)注意:numpy.ravel和ndarray.ravel以及ndarray.reshape(-1)等同。ndarray.flatten(order=‘C’)：返回坍塌成一維的數(shù)組的副本order：{‘C’,‘F’,‘A’,‘K’}，可選參數(shù)小結(jié)維