我有两个向量。第一个矢量名称为comments$author_id，第二个为enrolments$learner_id。我想在enrolmens数据框中添加新列，以显示每个comments$author_id行的enrolment$learner_id向量中重复行数。
示例：
if(enrolments$learner_id[1] repeated 5 times in comments$author_id)
enrolments$freqs[1] = 5
我可以不使用任何循环吗？
载体样品如下：
df1 <- data.frame(v1 = c(1,1,1,4,5,5,4,1,2,3,5,6,2,1,5,2,3,4,1,6,4,2,3,5,1,2,5,4))
df2 <- data.frame(v2 = c(1,2,3,4,5,6))
我想添加＆＃34;计数＆＃34;列到＆＃34; df2＆＃34;它显示了v1中重复的v2元素的计数。
答案 0 :(得分：1)
使用您的df1和df2示例，您可以这样做：
# Make data
df1 = data.frame(v1 = c(1,1,1,4,5,5,4,1,2,3,5,6,2,1,5,2,3,4,1,6,4,2,3,5,1,2,5,4))
df2 = data.frame(v2 = c(1,2,3,4,5,6))
# Add 'count' variable as reqeuested
df2$counts = sapply(df2$v2, function(x) {
sum(df1$v1 == x, na.rm = T) #na.rm=T just in case df1$v1 has missing values
})
df2 #view output
答案 1 :(得分：1)
您实际上在做的是聚合df1以获取计数，然后将此计数添加回df2集。这个逻辑可以很容易地转换成一堆不同的方法：
# base R
merge(
df2,
aggregate(cbind(df1[0], count=1), df1["v1"], FUN=sum),
by.x="v2", by.y="v1", all.x=TRUE
)
# data.table
library(data.table)
setDT(df1)
setDT(df2)
df2[df1[, .(count=.N), by=v1], on=c("v2"="v1")]
# dplyr
library(dplyr)
df1 %>%
group_by(v1) %>%
count() %>%
left_join(df2, ., by=c("v2"="v1"))
# v2 count
#1 1 7
#2 2 5
#3 3 3
#4 4 5
#5 5 6
#6 6 2
答案 2 :(得分：1)
＆＃34; [tabulate]给我这个错误：$＆lt; - 。data.frame（ tmp ，＆＃34; comments_count＆＃34;，value = c（0L， 0L，：替换有25596行数据 有25597＆＃34;
这很谨慎，因为<form name="userForm">
<div class="header-buttons3">
<button type="button" class="header-button-save btn" ng-disabled="userForm.$invalid" ng-click="submitUserForm()"><i class="fa fa-pencil"></i>SAVE</button>
<button type="button" class="header-button-cancel"><i class="fa fa-chevron-left"></i>CANCEL</button>
</div>
<div class="clearfix"></div>
<div class="row">
<div class="col-md-11 col-sm-12 col-xs-12">
<div class="x_content">
<br>
<div class="form-row row">
<div class="form-group required col-md-3">
<label for="first name" class="control-label">FIRST NAME</label>
<span class="after">*</span> <input class="form-control"
ng-class="{validbr: showfn==='false', invalidbr: showfn }"
ng-focus="showfn=false"
ng-blur="showfn=userForm.firstName.$invalid" id="firstname"
class="form-control" ng-model="user.firstName"
ng-pattern="/^[a-zA-Z]*$/" name="firstName" ng-maxlength="30"
maxlength="30" required placeholder="Enter First Name" />
<div style="color: Red"
ng-show="showfn && userForm.firstName.$error.required">Error
- First Name Required</div>
<div style="color: Red"
ng-show="showfn && userForm.firstName.$error.pattern">Error
- Enter only Character</div>
<div style="color: Red"
ng-show="showfn && userForm.firstName.$error.maxlength">Error
- Need 30 char max</div>
</div>
<div class="form-group required col-md-3">
<label for="last name" class="control-label">LAST NAME</label> <span
class="after">*</span> <input class="form-control"
ng-class="{validbr: showln==='false', invalidbr: showln }"
ng-focus="showln=false"
ng-blur="showln=userForm.lastName.$invalid" id="lastname"
ng-model="user.lastName" ng-pattern="/^[a-zA-Z]*$/"
name="lastName" ng-maxlength="50" maxlength="50" required
placeholder="Enter Last Name" />
<div style="color: Red"
ng-show="showln && userForm.lastName.$error.required">Error
- Last Name Required</div>
<div style="color: Red"
ng-show="showln && userForm.lastName.$error.pattern">Error
- Enter only Character</div>
<div style="color: Red"
ng-show="showln && userForm.lastName.$error.maxlength">Error
- Need 50 char max</div>
</div>
<div class="form-group required col-md-3">
<label for="inputEmail4" class="control-label">EMAIL
ADDRESS</label> <span class="after">*</span>
<input type="email" readonly class="form-control"
ng-class="{validbr: showem==='false', invalidbr: showem }"
ng-focus="showem=false"
ng-blur="showem=userForm.emailId.$invalid" id="emailId"
ng-model="user.emailId" name="emailId" ng-maxlength="70"
maxlength="70" required placeholder="Enter Email Address" />
<div style="color: Red"
ng-show="showem && userForm.emailId.$error.required">Error
- Email address Required</div>
<div style="color: Red"
ng-show="showem && userForm.emailId.$error.email">Error -
Not a valid email address</div>
</div>
<div class="form-group required col-md-3">
<label for="inputEmail4" class="control-label">USER STATUS
</label><br/>
<label>
<input type="radio" ng-model="user.active" ng-value="false">
IN ACTIVE
</label>
<label>
<input type="radio" ng-model="user.active" ng-value="true">
ACTIVE
</label>
</div>
</div>
<div class="form-row row">
<div class="form-group col-md-3">
<label for="mobile phone" class="col-form-label">MOBILE
PHONE</label> <input class="form-control" id="mobileNumber"
ng-class="{validbr: showmn==='false', invalidbr: showmn }"
ng-focus="showmn=false"
ng-blur="showmn=userForm.mobileNumber.$invalid"
ng-model="user.mobileNumber" name="mobileNumber"
ng-minlength="14" ng-maxlength="14" phone-input
placeholder="Enter Mobile Phone #" />
<div style="color: Red"
ng-show="showmn && userForm.mobileNumber.$error.minlength ">Error
- Need 10 digits for a Phone #</div>
<div style="color: Red"
ng-show="showmn && userForm.mobileNumber.$error.maxlength ">Error
- Need 10 digits for a Phone #</div>
<!-- <div ng-show="userForm.mobileNumber.$error.minlength">Error - Need 10 digits for a Phone #</div> -->
</div>
<div class="form-group col-md-3">
<label for="Desk Phone" class="col-form-label">DESK PHONE</label>
<input class="form-control" id="deskNumber"
ng-class="{validbr: showdn==='false', invalidbr: showdn }"
ng-focus="showdn=false"
ng-blur="showdn=userForm.deskNumber.$invalid" name="deskNumber"
ng-model="user.deskNumber" ng-minlength="14" maxlength="14"
phone-input placeholder="Enter Desk Phone #" />
<div style="color: Red"
ng-show="showdn && userForm.deskNumber.$error.minlength">Error
- Need 10 digits for a Phone #</div>
<div style="color: Red"
ng-show="showdn && userForm.deskNumber.$error.maxlength">Error
- Need 10 digits for a Phone #</div>
</div>
<div class="form-group">
<!-- <input type ="hidden" ng-model="user.createdBy" name="createdBy" />
<input type ="hidden" ng-model="user.updatedBy" name="updatedBy" /> -->
</div>
<!--
<input type="hidden" ng-value="user.createdBy" name="createdBy" />
<input type="hidden" ng-value="user.updatedBy" name="updatedBy" /> -->
</div>
</div>
</div>
</div>
</form>
末尾有一个值，而不是df2$v2的一部分 - 我将df1$v1和0添加到您的示例中以显示的是：
7要使用df1 <- data.frame(v1 = c(1,1,1,4,5,5,4,1,2,3,5,6,2,1,5,2,3,4,1,6,4,2,3,5,1,2,5,4))
df2 <- data.frame(v2 = c(1,2,3,0,4,5,6,7))
df2$count <- tabulate(factor(df1$v1, df2$v2))
# Error in `$<-.data.frame`(`*tmp*`, count, value = c(7L, 5L, 3L, 0L, 5L, :
# replacement has 7 rows, data has 8
进行更正，这可能是较大数据的最快解决方案：
tabulate有关该功能的文档，请参阅df2$count <- tabulate(factor(df1$v1, df2$v2), length(df2$v2))
df2
# v2 count
# 1 1 7
# 2 2 5
# 3 3 3
# 4 0 0
# 5 4 5
# 6 5 6
# 7 6 2
# 8 7 0
。