在 R 中外推时间序列数据 [英] extrapolate in R for a time-series data
问题描述
我有过去 20 年的时间序列数据.该变量每年都被测量,所以我有 20 个值.我有一个制表符分隔的文件,第一列代表年份,第二列代表值.这是它的样子:
<前>1991 4381992 4081993 3811994 3611995 3381996 3151997 2891998 2611999 2292000 2062001 1902002 1732003 1512004 1412005 1262006 1082007 992008 932009 852010 772011 712012 67我想推断未来几年第二列的价值.第二列中的值下降的速度也在下降,所以我认为我们不能使用线性回归.我想知道第二列将在哪一年接近零值.我从未使用过 R,所以如果您能帮助我编写用于从制表符分隔的文件中读取数据的代码,那就太好了.
谢谢
以下是可以帮助您入门的草图.
##获取数据tmp <- read.table(text="1991 4381992 4081993 3811994 3611995 3381996 3151997 2891998 2611999 2292000 2062001 1902002 1732003 1512004 1412005 1262006 1082007 992008 932009 852010 772011 712012 67", col.names=c("Year", "value"))图书馆(ggplot2)## 开发模型tmp$pred1 <- 预测(lm(价值〜poly(Year,2),数据= tmp))##查看数据p1 <- ggplot(tmp, aes(x = Year, y=value)) +geom_line() +geom_point() +geom_hline(aes(yintercept=0))打印(p1)##检查模型p1 +geom_line(aes(y = pred1), color="red")##基于模型外推pred <- data.frame(Year=1990:2050)pred$value <- 预测(lm(value ~ poly(Year, 2), data=tmp),newdata=pred)p1 +geom_line(颜色=红色",数据=预测)
在这种情况下,我们的模型说这条线永远不会过零.如果这没有意义,那么您将需要选择不同的模型.无论您选择何种模型,都可以将结果与数据一起绘制出来,这样您就可以了解自己的表现如何.
I have a time-series data for the last 20 years. The variable has been measured every year so I have 20 values. I have a tab-delimited file with first column representing year and second column the value. Here is what it looks like :
1991 438 1992 408 1993 381 1994 361 1995 338 1996 315 1997 289 1998 261 1999 229 2000 206 2001 190 2002 173 2003 151 2004 141 2005 126 2006 108 2007 99 2008 93 2009 85 2010 77 2011 71 2012 67
I want to extrapolate the value of second column for coming years. The rate at which values in second column is decreasing is also going down so I think we can't use linear regression. I wish to know in which year the second column will approach the value of zero. I have never used R so it would be great if you can even help me with code that will be used to read the data from a tab-delimited file.
Thanks
The following is a sketch that may help you get started.
## get the data
tmp <- read.table(text="1991 438
1992 408
1993 381
1994 361
1995 338
1996 315
1997 289
1998 261
1999 229
2000 206
2001 190
2002 173
2003 151
2004 141
2005 126
2006 108
2007 99
2008 93
2009 85
2010 77
2011 71
2012 67", col.names=c("Year", "value"))
library(ggplot2)
## develop a model
tmp$pred1 <- predict(lm(value ~ poly(Year, 2), data=tmp))
## look at the data
p1 <- ggplot(tmp, aes(x = Year, y=value)) +
geom_line() +
geom_point() +
geom_hline(aes(yintercept=0))
print(p1)
## check the model
p1 +
geom_line(aes(y = pred1), color="red")
## extrapolate based on model
pred <- data.frame(Year=1990:2050)
pred$value <- predict(lm(value ~ poly(Year, 2), data=tmp),newdata=pred)
p1 +
geom_line(color="red", data=pred)
In this case our model says the line will never cross zero. If that makes no sense then you'll want to pick a different model. Whatever model you pick, graph the result along with the data so you can see how well you're doing.
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