如何在插入符号中重现'train'对象的$ resample和$ result？

我是一个神奇的插入符号包的新手，并尝试使用重采样方法='timeslice'从lm模型中的train（）输出中重现一些对象 .

• 为什么我的例子中的$ result $ RMSE和$ result $ Rsquared与函数defaultSummary（$ pred $ pred，$ pred $ obs）的输出不同？

• 在$ resample中用什么数据来计算RMSE，Rsquared，MAE？

require(caret)
require(doParallel)

no_cores <- detectCores() - 1  
cls = makeCluster(no_cores)
registerDoParallel(cls)

data(economics)
#str(economics)
ec.data <- as.data.frame(economics[,-1]) #drop 'date' column
#head(ec.data)

#trainControl() with parallel processing and 1 step forecasts by TimeSlices------------------------
set.seed(123)
samplesCount = nrow(ec.data)
initialWindow  = 10
h = 1
s = 0
M = 1 # no of models that are evaluated during each resample (tuning parameters)

#seeds
resamplesCount = length(createTimeSlices(1:samplesCount, initialWindow, horizon = h, fixedWindow = TRUE, skip = s)$test)
seeds <- vector(mode = "list", length = resamplesCount + 1)   # length = B+1, B = number of resamples
for(i in 1:resamplesCount) seeds[[i]] <- sample.int(1000, M)  # The first B elements of the list should be vectors of integers of >= length M where M is the number of models being evaluated for each resample.
seeds[[(resamplesCount+1)]] <- sample.int(1000, 1) # The last element of the list only needs to be a single integer (for the final model)


trainCtrl.ec <- trainControl(
  method = "timeslice", initialWindow = initialWindow, horizon = h, skip = s,    # data splitting
  returnResamp = "all",
  savePredictions = "all",
  seeds = seeds,
  allowParallel = TRUE)


lm.fit.ec <- train( unemploy ~ ., data = ec.data,
                  method = "lm",
                  trControl = trainCtrl.ec)

lm.fit.ec
head(lm.fit.ec$resample)

输出：

> lm.fit.ec
Linear Regression 

574 samples
  4 predictor

No pre-processing
Resampling: Rolling Forecasting Origin Resampling (1 held-out with a fixed window) 
Summary of sample sizes: 10, 10, 10, 10, 10, 10, ... 
Resampling results:

  RMSE     Rsquared  MAE    
  250.072  NaN       250.072

Tuning parameter 'intercept' was held constant at a value of TRUE

为什么RMSE和Rsquared的输出与使用defaultSummary（）计算时的输出相同？

dat <- as.data.frame(cbind(lm.fit.ec$pred$pred, lm.fit.ec$pred$obs))
colnames(dat) <- c("pred", "obs")
defaultSummary(dat)

> defaultSummary(dat)
      RMSE   Rsquared        MAE 
394.440680   0.978365 250.072031

如何在$ resample中重现结果？

> head(lm.fit.ec$resample)
       RMSE Rsquared       MAE intercept    Resample
1  16.33273       NA  16.33273      TRUE Training010
2 232.16184       NA 232.16184      TRUE Training011
3 197.65143       NA 197.65143      TRUE Training012
4 393.29469       NA 393.29469      TRUE Training013
5 129.99157       NA 129.99157      TRUE Training014
6  60.95649       NA  60.95649      TRUE Training015

会话信息：

> sessionInfo()
R version 3.4.2 (2017-09-28)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)

Matrix products: default

locale:
[1] LC_COLLATE=Swedish_Sweden.1252  LC_CTYPE=Swedish_Sweden.1252    LC_MONETARY=Swedish_Sweden.1252
[4] LC_NUMERIC=C                    LC_TIME=Swedish_Sweden.1252    

attached base packages:
[1] parallel  stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
 [1] fpp_0.5             tseries_0.10-42     lmtest_0.9-35       zoo_1.8-0          
 [5] expsmooth_2.3       fma_2.3             forecast_8.2        mlbench_2.1-1      
 [9] spikeslab_1.1.5     randomForest_4.6-12 lars_1.2            doParallel_1.0.11  
[13] iterators_1.0.8     foreach_1.4.3       caret_6.0-77.9000   ggplot2_2.2.1      
[17] lattice_0.20-35