创建具有15个位置的样本矢量

Question

我为5个科目创建了15名学生的分数。我还在每个主题中创建了一个标记向量。我想根据矢量密码中给定的值用“通过”或“失败”来改变标记的每一列...我已经能够手动操作，但是我想使用一些循环功能，以便将密码映射到列上然后进行变异使用“通过”或“失败”创建新列或新数据框。

创建具有15个位置的样本矢量

x <- runif(15)
#convert to DF
marks <- as.data.frame(x)
marks[1:5] <- sapply(1:5, "+", rnorm(5,60,15))
names(marks) <- paste0("sub", 1:5)
marks
colMeans(marks)
lapply(marks, range)
lapply(marks, is.na)
colSums(is.na(marks))
marks1 = round(marks,2)
passmarks = c(60, 65, 62,70, 45)
names(marks1)
marks1 %>% mutate(sub1a = ifelse(sub1 <= passmarks[1], 'F','P'), sub2a = ifelse(sub2 <= passmarks[2], 'F','P'), sub3a = ifelse(sub3 <= passmarks[3], 'F','P'), sub4a = ifelse(sub4 <= passmarks[4], 'F','P'), sub5a = ifelse(sub5 <= passmarks[5], 'F','P'))


marks1 %>% summarise_at(vars(sub1:sub5), mean, na.rm=T)
marks1 %>% mutate_all(funs(./75))

问题的第二部分：：：：问题的这一阶段已解决。我必须为每个学生计算SGPA。如果我有分数，我会给每个学生科目分配分数。这取决于每个主题的平均值和特定序列的标准差。该等级取决于每列标记的均值和所有列均相同的std值。接下来，如果我们有成绩，我们必须计算获得的总成绩积分。对于每个主题列，都有已知的学分。还已知每个年级的年级分数。我想为每个学生计算学分的数字总和。.我尝试对其中的一部分进行编码...我将寻求您的帮助，以使其变得更简单，更优雅...

#continued
#find mean of each subject
(meanx = colMeans(marks1))
#(sdx=apply(marks1,2,sd))
(sd1 = seq(1.5, -2,-.5)) #this pattern is same across all subjects
#these are the grades associated with each Std Dev
(names(sd1) = c('AP','A','AM','BP','B','BM','CP','C'))
sd1
sd1['AP']  #test for A+

    #this is sample vectorise function created: here meanx should be replace with respective mean of the subject 
    RgradeAssigned = function(x) { ifelse(x >= meanx * sd1['AP'],'AP', ifelse(x >= meanx + sd1['A'], 'A', ifelse(x >= meanx + sd1['AM'], 'AM', ifelse(x >= meanx + sd1['BP'], 'BP', ifelse(x >= meanx * sd1['B'], 'B',ifelse(x >= meanx + sd1['BM'], 'BM',ifelse(x >= meanx + sd1['CP'], 'CP',ifelse(x >= meanx + sd1['C'], 'C', 'F'))))))))}
    RgradeAssigned(marks1)
    #meanx should mean from the vector meanx : for sub1 it should be meanx[1]
    meanx

    #Calculate SGPA
    #credit for each subject 
    (subcredits = c(3,2,4,3,3))
    #gradepoints with wrt to each grade
    gradeName = c('AP','A','AM','BP','B','BM','CP','C','F')
    gradePoint = c(10,9,8,7,6,5,4,3,0)
    names(gradePoint) = gradeName
    gradePoint
    # if a particular grade, find grade point -> multiply by subject credit -> for each student -> find sum of grades ie sum each row
    # for eg row grade were
    #'AP','A','AM','BP','B' -> 10,9,8,7,6 -> 10*3 + 9*2+ 8*4 + 7*3 + 6*3 
    #subject credits : 3,2,4,3,3

    #Now Mapping of Grade to Point is available

Answer 1

您可以使用mapply，即

mapply(`<`, passmarks, marks1)

给出，

       [,1]  [,2]  [,3]  [,4] [,5]
 [1,] FALSE FALSE FALSE FALSE TRUE
 [2,] FALSE FALSE FALSE FALSE TRUE
 [3,] FALSE FALSE FALSE FALSE TRUE
 [4,]  TRUE  TRUE  TRUE FALSE TRUE
 [5,] FALSE FALSE FALSE FALSE TRUE
 [6,] FALSE FALSE FALSE FALSE TRUE
 [7,] FALSE FALSE FALSE FALSE TRUE
 [8,] FALSE FALSE FALSE FALSE TRUE
 [9,]  TRUE  TRUE  TRUE FALSE TRUE
[10,] FALSE FALSE FALSE FALSE TRUE
[11,] FALSE FALSE FALSE FALSE TRUE
[12,] FALSE FALSE FALSE FALSE TRUE
[13,] FALSE FALSE FALSE FALSE TRUE
[14,]  TRUE FALSE  TRUE FALSE TRUE
[15,] FALSE FALSE FALSE FALSE TRUE

要获得具有PASS和FAIL的矩阵，可以采用的一种方法是

matrix(c('FAIL', 'PASS')[mapply(`<`, passmarks, marks1) + 1], ncol = ncol(marks1))

根据情况使用Dply消除突变

创建具有15个位置的样本矢量

1 个答案: