How to change type of line in prophet plot?

问题

Facebook's Prophet in R (there's also a Python version) is used to generate time series forecasts.

A model m is created by:

m <- prophet(df)
future <- make_future_dataframe(m, periods = 365)
forecast <- predict(m, future)
plot(m, forecast)

Which returns a very nicely formatted graph, like:

I would like to change the line type, to get not dots but a usual thin line.

I had tried this

lines(m$history$y,lty=1)

but got an error

 In doTryCatch(return(expr), name, parentenv, handler)

Are there are any suggestions how to convert those dots into a line?

回答1:

The plot method for prophet objects uses ggplot2, so base R graphics functions like lines() won't work. You can use ggplot2::geom_line() to add lines, but at the moment I don't see an easy way to replace the points by lines ...

Example from ?prophet:

history <- data.frame(ds = seq(as.Date('2015-01-01'), as.Date('2016-01-01'), by = 'd'),
                           y = sin(1:366/200) + rnorm(366)/10)
     m <- prophet(history)
future <- make_future_dataframe(m, periods = 365)
forecast <- predict(m, future)
pp <- plot(m,forecast)

Add lines:

library(ggplot2)
pp + geom_line()

This question provides a (hacky) way forward:

pp2 <- pp + geom_line()
qq2 <- ggplot_build(pp2)
qq2$data[[2]]$colour <- NA
plot(ggplot_gtable(qq2))

But obviously something went wrong with the hack. The better bet would be to look at the plot method(prophet:::plot.prophet) and modify it to behave as you want ... Here is the bare-bones version:

df <- prophet:::df_for_plotting(m, forecast)
gg <-ggplot(df, aes(x = ds, y = y)) + labs(x = "ds", y = "y")
gg <- gg + geom_ribbon(ggplot2::aes(ymin = yhat_lower, 
        ymax = yhat_upper), alpha = 0.2, fill = "#0072B2", 
        na.rm = TRUE)
## replace first geom_point() with geom_line() in next line ...
gg <- gg + geom_line(na.rm = TRUE) + geom_line(aes(y = yhat), 
    color = "#0072B2", na.rm = TRUE) + theme(aspect.ratio = 3/5)

I may have stripped out some components that exist in your data/forecast, though ...

回答2:

it is possible to make such manipulations with dyplot.prophet(m, forecast) (html version of plot) :) before that, we should rewrite function like here:

dyplot.prophet <- function(x, fcst, uncertainty=TRUE, 
                           ...) 
{
  forecast.label='Predicted'
  actual.label='Actual'
  # create data.frame for plotting
  df <- prophet:::df_for_plotting(x, fcst)

  # build variables to include, or not, the uncertainty data
  if(uncertainty && exists("yhat_lower", where = df))
  {
    colsToKeep <- c('y', 'yhat', 'yhat_lower', 'yhat_upper')
    forecastCols <- c('yhat_lower', 'yhat', 'yhat_upper')
  } else
  {
    colsToKeep <- c('y', 'yhat')
    forecastCols <- c('yhat')
  }
  # convert to xts for easier date handling by dygraph
  dfTS <- xts::xts(df %>% dplyr::select_(.dots=colsToKeep), order.by = df$ds)

  # base plot
  dyBase <- dygraphs::dygraph(dfTS)

  presAnnotation <- function(dygraph, x, text) {
    dygraph %>%
      dygraphs::dyAnnotation(x, text, text, attachAtBottom = TRUE)
  }

  dyBase <- dyBase %>%
    # plot actual values
    dygraphs::dySeries(
      'y', label=actual.label, color='black',stepPlot = TRUE, strokeWidth=1
    ) %>%
    # plot forecast and ribbon
    dygraphs::dySeries(forecastCols, label=forecast.label, color='blue') %>%
    # allow zooming
    dygraphs::dyRangeSelector() %>% 
    # make unzoom button
    dygraphs::dyUnzoom()
  if (!is.null(x$holidays)) {
    for (i in 1:nrow(x$holidays)) {
      # make a gray line
      dyBase <- dyBase %>% dygraphs::dyEvent(
        x$holidays$ds[i],color = "rgb(200,200,200)", strokePattern = "solid")
      dyBase <- dyBase %>% dygraphs::dyAnnotation(
        x$holidays$ds[i], x$holidays$holiday[i], x$holidays$holiday[i],
        attachAtBottom = TRUE)
    }
  }
  return(dyBase)
}

the strokeWidth=0 was before and we have changed it to strokeWidth=1 and added stepPlot = TRUE

the whole basis code is situated here: https://rdrr.io/cran/prophet/src/R/plot.R

来源：https://stackoverflow.com/questions/53947623/how-to-change-type-of-line-in-prophet-plot

标签

facebook-prophet