Na.fail.default 使用交叉验证的最佳 k 错误

Question

我正在处理威斯康星乳腺癌诊断的数据集。 (https://www.kaggle.com/uciml/breast-cancer-wisconsin-data)

我正在使用使用 kNN 的交叉验证来计算 k 的最佳值。

我将 csv 文件读入 wbcd，当我运行下面的代码时，我得到以下错误：

fit <- train(diagnosis ~ ., method = "knn", tuneGrid = expand.grid(k = 1:50), trControl= trControl, metric = "Accuracy", data = wbcd)
plot(fit)

错误 na.fail.default(list(diagnosis = c("M", "M", "M", "M", "M", "M", : 对象中缺少值

我在数据集中的诊断字段中没有看到任何缺失值。知道是什么原因造成的吗？

Answer 1

我注意到最后一列很奇怪..所以要重现错误：

library(caret)
wbcd = read.csv("datasets_180_408_data.csv",stringsAsFactors=FALSE)
fit <- train(diagnosis ~ ., method = "knn", tuneGrid = expand.grid(k = 1:50),
trControl= trainControl(method="cv",number=10), metric = "Accuracy", data = wbcd[,-1])

Error in na.fail.default(list(diagnosis = c("M", "M", "M", "M", "M", "M",  : 
  missing values in object

如果您查看摘要：

summary(wbcd)
[...]
 concavity_worst  concave.points_worst symmetry_worst   fractal_dimension_worst
 Min.   :0.0000   Min.   :0.00000      Min.   :0.1565   Min.   :0.05504        
 1st Qu.:0.1145   1st Qu.:0.06493      1st Qu.:0.2504   1st Qu.:0.07146        
 Median :0.2267   Median :0.09993      Median :0.2822   Median :0.08004        
 Mean   :0.2722   Mean   :0.11461      Mean   :0.2901   Mean   :0.08395        
 3rd Qu.:0.3829   3rd Qu.:0.16140      3rd Qu.:0.3179   3rd Qu.:0.09208        
 Max.   :1.2520   Max.   :0.29100      Max.   :0.6638   Max.   :0.20750        
    X          
 Mode:logical
 NA's:569

如果你取出最后一列，还要注意不要与id列对齐（因此wbcd[,-1]），效果很好：

wbcd$X = NULL
fit <- train(diagnosis ~ ., method = "knn", 
tuneGrid = expand.grid(k = 1:50), 
trControl= trainControl(method="cv",number=10), 
metric = "Accuracy", data = wbcd[,-1])

fit
k-Nearest Neighbors 

569 samples
 30 predictor
  2 classes: 'B', 'M' 

No pre-processing
Resampling: Cross-Validated (10 fold) 
Summary of sample sizes: 512, 513, 511, 512, 513, 512, ... 
Resampling results across tuning parameters:

  k   Accuracy   Kappa    
   1  0.9156231  0.8174624
   2  0.9085407  0.8013572
   3  0.9263039  0.8415912
   4  0.9263342  0.8415714
   5  0.9314752  0.8520796
   6  0.9279665  0.8451175
   7  0.9297511  0.8489385
   8  0.9296582  0.8476492

[...]

Na.fail.default 使用交叉验证的最佳 k 错误

Na.fail.default error for best k using cross validation

r

cross-validation

r-caret

knn