使用列中的信息在r中创建新列

Question

我有一个像这样的数据集：

record <- c("2000-01-22","2001-01-22","2002-01-22")
brand <- c("blue","red","yellow")
sale <- c("5","42","54")
mydf <- data.frame(record,brand,sale)
mydf

      record  brand sale
1 2000-01-22   blue    5
2 2001-01-22    red   42
3 2002-01-22 yellow   54

我想创建一个名为＆＃34; year＆＃34;的新列。仅包括不同的年份，例如：

   record     brand sale  year
1 2000-01-22   blue    5  2000
2 2001-01-22    red   42  2001
3 2002-01-22 yellow   54  2002

非常感谢您的帮助。

巴兹

Answer 1

您可以使用lubridate::year：

执行此操作

library(lubridate)

mydf$year <- year(as.Date(mydf$record))
> mydf
      record  brand sale year
1 2000-01-22   blue    5 2000
2 2001-01-22    red   42 2001
3 2002-01-22 yellow   54 2002

Answer 2

不使用其他包。 <怎么样

public class Point3D {
    public int x, y, z;

    public static List<Point3D> allWithinRange(List<Point3D> possiblePoints, int x, int y, int z, int inter) {
        List<Point3D> list = new ArrayList<Point3D>(possiblePoints.size());
        possiblePoints.stream()
                .filter(it -> it.x <= x + inter && it.x >= x - inter)
                .filter(it -> it.y <= y + inter && it.y >= y - inter)
                .filter(it -> it.z <= z + inter && it.z >= z - inter)
                .forEach(list::add);
        return list;
    }
}