说明：  实验将Iris花的数据集分为2组，每组各75个样本，每组中每种花各有25个样本。其中一组作为以上程序的训练样本，另外一组作为检验样本。为了方便训练，将3类花分别编号为1，2，3 。 　　使用这些数据训练一个4输入（分别对应4个特征），3输出（分别对应该样本属于某一品种的可能性大小）的前向网络。
(The data set of Iris flower was divided into 2 groups, 75 samples in each group. Each group had 25 samples per flower. One group is the training sample for the above procedure, and the other one is the test sample. To facilitate training, 3 kinds of flowers were numbered 1, 2 and 3, respectively. Use these data to train a forward network with a 4 input (4 features respectively), and 3 output (for the size of the sample that belongs to a certain variety, respectively).)