代码运行出错,检查对函数 'labels' 的调用中是否缺失参数或参数数据类型不正确

% 归一化特征
normalizedFeatures = (features - mean(features, 1)) ./ std(features, 1);
 
% 准备训练和测试数据
trainRatio = 0.8;
[trainInd, ~, testInd] = dividerand(size(normalizedFeatures, 1), trainRatio, 0, 1 - trainRatio);
trainData = normalizedFeatures(trainInd, :);
trainLabels = labels(trainInd);
testData = normalizedFeatures(testInd, :);
testLabels = labels(testInd);

代码运行出错,检查对函数 'labels' 的调用中是否缺失参数或参数数据类型不正确,如何操作

“./” 这个符号是干啥的?