执行下面语句 时，报错
> matplot(x = Time, y = creditspreads, type = 'l', xlab = 'Maturity', ylab = 'Credit spreads', main = 'Term structure of credit spreads in the Merton model')Error in as.matrix(y) : object 'creditspreads' not found；
这个该怎么解决呢 ？
通常情况下如果程序报objects找不到，怎么判断应该安装哪个 library或者哪个packages呢？