ext/libsvm/svm.cpp in rb-libsvm-1.1.3 vs ext/libsvm/svm.cpp in rb-libsvm-1.1.4

@@ -2046,10 +2046,28 @@
 			count[nr_class] = 1;
 			++nr_class;
 		}
 	}
 
+	//
+	// Labels are ordered by their first occurrence in the training set. 
+	// However, for two-class sets with -1/+1 labels and -1 appears first, 
+	// we swap labels to ensure that internally the binary SVM has positive data corresponding to the +1 instances.
+	//
+	if (nr_class == 2 && label[0] == -1 && label[1] == 1)
+	{
+		swap(label[0],label[1]);
+		swap(count[0],count[1]);
+		for(i=0;i<l;i++)
+		{
+			if(data_label[i] == 0)
+				data_label[i] = 1;
+			else
+				data_label[i] = 0;
+		}
+	}
+
 	int *start = Malloc(int,nr_class);
 	start[0] = 0;
 	for(i=1;i<nr_class;i++)
 		start[i] = start[i-1]+count[i-1];
 	for(i=0;i<l;i++)
@@ -2319,15 +2337,20 @@
 
 // Stratified cross validation
 void svm_cross_validation(const svm_problem *prob, const svm_parameter *param, int nr_fold, double *target)
 {
 	int i;
-	int *fold_start = Malloc(int,nr_fold+1);
+	int *fold_start;
 	int l = prob->l;
 	int *perm = Malloc(int,l);
 	int nr_class;
-
+	if (nr_fold > l)
+	{
+		nr_fold = l;
+		fprintf(stderr,"WARNING: # folds > # data. Will use # folds = # data instead (i.e., leave-one-out cross validation)\n");
+	}
+	fold_start = Malloc(int,nr_fold+1);
 	// stratified cv may not give leave-one-out rate
 	// Each class to l folds -> some folds may have zero elements
 	if((param->svm_type == C_SVC ||
 	    param->svm_type == NU_SVC) && nr_fold < l)
 	{
@@ -2743,12 +2766,12 @@
 	svm_model *model = Malloc(svm_model,1);
 	svm_parameter& param = model->param;
 	model->rho = NULL;
 	model->probA = NULL;
 	model->probB = NULL;
+	model->sv_indices = NULL;
 	model->label = NULL;
 	model->nSV = NULL;
-    model->sv_indices = NULL;
 
 	char cmd[81];
 	while(1)
 	{
 		fscanf(fp,"%80s",cmd);