我的df的简短版本如下：
A <- c(10,50,50,10,60,70,50,20,60,10)
B <- c(0,3,2,4,1,3,5,1,1,2)
df<- data.frame(A,B)
df
A B
10 0
50 3
50 2
10 4
60 1
70 3
50 5
20 1
60 1
10 2
我想根据A列的某些条件和B列中的值生成输出C.
条件：
以下是C列中我想要的一个例子：
A B C Explaination
10 0 0 A <50, so C=0
50 3 0 A just becomes >= 50, so C is still 0
50 2 1 We have two consecutive A >= 50, so C = abs(2-3) = 1
10 4 0 A <50, so C=0
60 1 0 A just becomes >= 50, so C is still 0
70 3 2 We have two consecutive A >= 50, so C = abs(3-1) = 2
50 5 2 consecutive rows with A >= 50, so C = abs(5-3) = 2
20 1 0 A <50, so C=0
60 1 0 A just becomes >= 50, so C is still 0
10 2 0 A <50, so C=0
答案 0 :(得分：1)
这是一个选项，虽然逻辑有点啰嗦：
df$C <- ifelse(df$A < 50 | (df$A >= 50 & c(0, head(df$A, -1)) < 50) ,
0, c(NA, abs(diff(df$B))))
说明：
ifelse(df$A < 50, 0, c(NA, abs(diff(df$B))))开始。如果A < 50，则给出0，否则B的差异（diff(B)是一个短于B的元素，所以我在NA上加A前）。c(0, head(df$A, -1))首次超过50的情况，其中值仍应为0。注意2:end只是A列的元素0，前面有A - 它是df$A >= 50的“上一个”值。因此，如果< 50和之前的值为import javafx.application.Application;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.SelectionMode;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.VBox;
import javafx.scene.text.Text;
import javafx.stage.Stage;
public class TableCopyPasteCellsDemo extends Application {
private final ObservableList<Person> data = FXCollections.observableArrayList(new Person("Jacob", "Smith", 18), new Person("Isabella", "Johnson", 19), new Person("Ethan", "Williams", 20), new Person("Michael", "Brown", 21));
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage stage) {
stage.setWidth(500);
stage.setHeight(550);
// create table columns
TableColumn<Person, String> firstNameCol = new TableColumn<Person, String>("First Name");
firstNameCol.setMinWidth(100);
firstNameCol.setCellValueFactory(new PropertyValueFactory<Person, String>("firstName"));
// firstNameCol.setVisible(false); // hide column for testing view/model indices
TableColumn<Person, String> lastNameCol = new TableColumn<Person, String>("Last Name");
lastNameCol.setMinWidth(100);
lastNameCol.setCellValueFactory(new PropertyValueFactory<Person, String>("lastName"));
TableColumn<Person, Integer> ageCol = new TableColumn<Person, Integer>("Age");
ageCol.setMinWidth(60);
ageCol.setCellValueFactory(new PropertyValueFactory<Person, Integer>("age"));
TableView<Person> table = new TableView<>();
table.setPlaceholder(new Text("No content in table"));
table.setItems(data);
table.getColumns().addAll(firstNameCol, lastNameCol, ageCol);
final VBox vbox = new VBox();
vbox.setSpacing(5);
vbox.setPadding(new Insets(10, 10, 10, 10));
BorderPane borderPane = new BorderPane();
borderPane.setCenter(table);
vbox.getChildren().addAll(borderPane);
vbox.getChildren().add( new Label( "Select cells and press CTRL+C. Paste the data into Excel or Notepad"));
Scene scene = new Scene(vbox);
stage.setScene(scene);
stage.show();
// enable multi-selection
table.getSelectionModel().setCellSelectionEnabled(true);
table.getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);
// enable copy/paste
TableUtils.installCopyPasteHandler(table);
}
public static class Person {
private final StringProperty firstName;
private final StringProperty lastName;
private final IntegerProperty age;
private Person(String fName, String lName, Integer age) {
this.firstName = new SimpleStringProperty(fName);
this.lastName = new SimpleStringProperty(lName);
this.age = new SimpleIntegerProperty(age);
}
public final StringProperty firstNameProperty() {
return this.firstName;
}
public final java.lang.String getFirstName() {
return this.firstNameProperty().get();
}
public final void setFirstName(final java.lang.String firstName) {
this.firstNameProperty().set(firstName);
}
public final StringProperty lastNameProperty() {
return this.lastName;
}
public final java.lang.String getLastName() {
return this.lastNameProperty().get();
}
public final void setLastName(final java.lang.String lastName) {
this.lastNameProperty().set(lastName);
}
public final IntegerProperty ageProperty() {
return this.age;
}
public final int getAge() {
return this.ageProperty().get();
}
public final void setAge(final int age) {
this.ageProperty().set(age);
}
}
}
，那么这是我们第一次超过50，我们应该得到值0. 我相信还有其他方法可以做到。
答案 1 :(得分：0)
library(dplyr)
df%>%mutate(C=ifelse(A<50,0,(ifelse(A>=50 & lag(A)>=50,abs(B-lag(B)),0))))