关于使用R型包的R中svm的一些问题

Question

我需要一些帮助来了解以下代码的结果：

library(caret)
ctrl <- trainControl(method = "cv", savePred=T)
mod <- train(Sepal.Length~., data=iris, method = "svmRadial", trControl = ctrl) 
#pred_test <-predict(mod,iris)
head(mod$pred)
mod

这是结果：

      pred obs rowIndex    sigma    C Resample
1 4.879055 4.7       30 1.781273 0.25   Fold01
2 5.230893 4.9       38 1.781273 0.25   Fold01
3 5.268827 5.0       44 1.781273 0.25   Fold01
4 4.947738 5.0       50 1.781273 0.25   Fold01
5 6.085828 6.6       76 1.781273 0.25   Fold01
6 5.524783 5.7       80 1.781273 0.25   Fold01

Support Vector Machines with Radial Basis Function Kernel 

150 samples
  4 predictor

No pre-processing
Resampling: Cross-Validated (10 fold) 
Summary of sample sizes: 135, 135, 136, 135, 136, 136, ... 
Resampling results across tuning parameters:

  C     RMSE       Rsquared   MAE      
  0.25  0.4670729  0.7307655  0.3478073
  0.50  0.4376385  0.7559361  0.3300692
  1.00  0.4185441  0.7755009  0.3144116

问题1：pred是什么？ 问题2：Rsquared是什么？

谢谢！