only size-1 arrays can be converted to Python scalars

python版本：3.6.5

opencv版本：3.2.0

使用的jupyter notebook

源码以下：

import cv2 import numpy as np import matplotlib.pyplot as plt %matplotlib inline # Feature set containing (x,y) values of 25 known/training data
trainData = np.random.randint(0,100,(25,2)).astype(np.float32) # Labels each one either Red or Blue with numbers 0 and 1
responses = np.random.randint(0,2,(25,1)).astype(np.float32) # Take Red families and plot them
red = trainData[responses.ravel()==0] plt.scatter(red[:,0],red[:,1],80,'r','^') # Take Blue families and plot them
blue = trainData[responses.ravel()==1] plt.scatter(blue[:,0],blue[:,1],80,'b','s') # plt.show()
 newcomer = np.random.randint(0,100,(1,2)).astype(np.float32) plt.scatter(newcomer[:,0],newcomer[:,1],80,'g','o') knn = cv2.ml.KNearest_create() knn.train(trainData,responses) ret, results, neighbours ,dist = knn.findNearest(newcomer, 3) print ("result: ", results,"\n") print ("neighbours: ", neighbours,"\n") print ("distance: ", dist) plt.show()

错误以下：

--------------------------------------------------------------------------- TypeError Traceback (most recent call last) <ipython-input-21-b1c5cdca5e57> in <module>() 20 knn = cv2.ml.KNearest_create() 21 
---> 22 knn.train(trainData,responses) 23 ret, results, neighbours ,dist = knn.findNearest(newcomer, 3) 24 TypeError: only size-1 arrays can be converted to Python scalars

错误缘由：

传递的参数错误

train函数中第二个参数应该是数组的布局方式

应该根据传入数组的形式填cv2.ml.ROW_SAMPLE或者cv2.ml.COL_SAMPLE

例如个人就是

knn.train(trainData,cv2.ml.ROW_SAMPLE，responses)

参考地址：https://stackoverflow.com/questions/33975695/type-error-only-length-1-arrays-can-be-converted-to-python-scalars