我正在拟合208个泉水的人口数据的指数模型,以便以5年为间隔反映1975 - 2015年的人口数量,即seq(1975,2015,5)
。这是我的数据集中的前5个弹簧以及我用来拟合模型并绘制它的代码(我希望得到数字):
springsheds <-
structure(list(spring = c("alexander", "alexander", "alexander", "alexander",
"blue hole", "blue hole", "blue hole", "blue hole", "cedar head", "cedar head",
"cedar head", "cedar head", "charles", "charles", "charles", "charles",
"columbia", "columbia", "columbia", "columbia"), year = c(2000L, 2005L, 2010L,
2015L, 2000L, 2005L, 2010L, 2015L, 2000L, 2005L, 2010L, 2015L, 2000L, 2005L,
2010L, 2015L, 2000L, 2005L, 2010L, 2015L), pop = c(527L, 620L, 732L, 867L,
3071L, 3356L, 3669L, 4007L, 3038L, 3320L, 3630L, 3965L, 1311L, 1446L, 1592L,
1747L, 7550L, 8130L, 8706L, 9332L)), .Names = c("spring", "year", "pop"),
class = "data.frame", row.names = c(NA, -20L))
models.spsh <- by(springsheds, springsheds$spring, function(x) {
fm <- lm(log(pop) ~ year, data = x)
timevalues <- seq(1970, 2020, 10)
predict <- exp(predict(fm,list(year=timevalues)))
plot(pop ~ year, x, main = spring[1], xlim = c(1970, 2020), ylim=c(0,15000))
lines(timevalues, predict,lwd=1, col = "blue", xlab = "Year", ylab = "Population")
})
我还可以使用by()来提取每个春天的预测值吗?我目前的解决方法是分别为每个弹簧创建一个对象,并迭代地将预测值添加到对象:
fm <- lm(log(pop) ~ year, data = alex)
timevalues <- seq(1975,2015,5)
alex <- exp(predict(fm,list(year=timevalues)))
old<-cbind(timevalues,alex)
fm <- lm(log(pop) ~ year, data = blue)
blue <- exp(predict(fm,list(year=timevalues)))
old<-cbind(old,blue)
这看起来效率非常低,而且我假设有更优雅的方式来实现这一点,有没有一种方法可以添加到我的初始代码中来提取预测的人口值?
答案 0 :(得分:2)
您可以split
数据,然后对每个所需的输出使用lapply
:
#Split the data grouped by spring
sdata <- split(springsheds, springsheds$spring)
#Fit the models
fit.spsh <- lapply(sdata, function(x) {
lm(log(pop) ~ year, data = x)
})
#Get the predicted values
timevalues <- seq(1970, 2020, 10)
predictList <- lapply(fit.spsh, function(m) exp(predict(m,list(year=timevalues))))
#Generate plots
lapply(names(sdata), function(n) {
plot(pop ~ year,sdata[[n]] , main = n, xlim = c(1970, 2020), ylim=c(0,15000))
lines(timevalues, predictList[[n]],lwd=1, col = "blue", xlab = "Year", ylab = "Population")
})
#Combine the predict values
do.call(cbind,predictList)
#alexander blue hole cedar head charles columbia
#1 194.3679 1803.470 1783.068 738.9545 4955.633
#2 270.8778 2153.663 2129.682 894.9253 5705.076
#3 377.5048 2571.856 2543.676 1083.8167 6567.857
#4 526.1037 3071.253 3038.146 1312.5774 7561.118
#5 733.1965 3667.621 3628.738 1589.6225 8704.590
#6 1021.8081 4379.790 4334.137 1925.1434 10020.989