Gentlemen,
Thank you so much for your help. You have solved my problem.
> Using Achim's d this also works to generate z where FUN is a function used
> to transform the index column and format is also passed to FUN.
>
> z <- read.zoo(d, index = "time", FUN = as.yearqtr, format = "Q%q %Y")
>
> On Sun, Jan 28, 2018 at 4:53 PM, Achim Zeileis <achim.zeil...@uibk.ac.at>
> wrote:
>> On Sun, 28 Jan 2018, p...@philipsmith.ca wrote:
>>
>>> I have a data set with quarterly time series for several variables. The
>>> time index is recorded in column 1 of the dataframe as a character
>>> vector
>>> "Q1 1961", "Q2 1961","Q3 1961", "Q4 1961", "Q1 1962", etc. I want to
>>> produce
>>> line plots with ggplot2, but it seems I need to convert the time index
>>> from
>>> character to date class. Is that right? If so, how do I make the
>>> conversion?
>>
>>
>> You can use the yearqtr class in the zoo package, converting with
>> as.yearqtr(..., format = "Q%q %Y"). zoo also provides an autoplot()
>> method
>> for ggplot2-based time series visualizations. See ?autoplot.zoo for
>> various
>> examples.
>>
>> ## example data similar to your description
>> d <- data.frame(sin = sin(1:8), cos = cos(1:8))
>> d$time <- c("Q1 1961", "Q2 1961", "Q3 1961", "Q4 1961", "Q1 1962",
>> "Q2 1962", "Q3 1962", "Q4 1962")
>>
>> ## convert to zoo series
>> library("zoo")
>> z <- zoo(as.matrix(d[, 1:2]), as.yearqtr(d$time, "Q%q %Y"))
>>
>> ## ggplot2 display
>> library("ggplot2")
>> autoplot(z)
>>
>> ## with nicer axis scaling
>> autoplot(z) + scale_x_yearqtr()
>>
>> ## some variations
>> autoplot(z, facets = Series ~ .) + scale_x_yearqtr() + geom_point()
>> autoplot(z, facets = NULL) + scale_x_yearqtr() + geom_point()
>>
>>
>>
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>>
>> ______________________________________________
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>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
>
>
> --
> Statistics & Software Consulting
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>
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