how to save plot with `file` para with a `tpar` multiplot

[SungManhin]

# plot layout
tpar(mfrow=c(2,1))

tinyplot(X_new, mean_coverage_rate, 
         xlab="local test point", ylab="coverage rate",
         ylim=c(0, 1.0),
         col="forestgreen",
         draw=abline(h=1-alpha, col="orangered", lwd=1.2),
         main="Local coverage with kernel estimation", sub="estimator")


tinyplot(X_new, beta_hat*X_new, 
         xlab="local test point", ylab="prediction interval",
         col="forestgreen", 
         sub="Coverage in one trial",
         draw={
           segments(x0=X_new, y0=beta_hat*X_new-half_interval[, 1],
                    x1=X_new, y1=beta_hat*X_new+half_interval[, 1],
                    lwd=2, col="forestgreen")
           points(X_new, X_new+rnorm(40, sd=0.1), pch=17, col="gold1")
         },
        file="/Users/desktop/a.jpg"
         )

hi, I'm wondering how to save plot with file para with such a tpar layout above, it seems that tinyplot always save a png for the 2nd plot seperately...

[zeileis]

I think that this is currently not possible. If file = ... is specified, then tinyplot() opens a graphics device at the beginning of the code it runs and closes it when the function is finished. Thus, only the code of a single tinyplot() call is recorded in the plotting device. There is (AFAICS) currently no way for this one call to recreate previous calls on a different device.

The same applies to tinyplot_add() which cannot be combined with the file = ... argument to record a combined graphics from multiple calls.

I'm leaving this open for a bit just in order to see whether Grant @grantmcdermott has further ideas/advice.

[SungManhin]

Thx! The combination of plots using par is more of base-R plot style than using facet by group indicators, and tinyplot may ignore this when it comes to issues about saving the figure. Hope for modifications.

[grantmcdermott]

Yeah, unfortunately we don't have a good way to use file with multiple plots/layers. Ofc the base solution is simply to open a new png() device manually and then call dev.off() to save.

It would be cool if we could find a "native" tinyplot way to invoke file saving with multiple layers and/or plots. It would probably require an extra argument (hold?) that prevents the device from being closed automatically and that the user explicitly close with dev.off() themselves.

Edit: actually, with an extra hold argument, this should work:

plt(..., file = 'myplot.png', hold = TRUE)
plt_add(..., hold = FALSE)

Open to other suggestions...

[vincentarelbundock]

Frankly, I think we should just add a note to the @param file documentation to indicate this limitation.

Supporting multi-plot with this argument is likely to complicate the code base significantly, and there's a perfectly fine/easy solution in base R. So I think we should document and close.

[SungManhin]

Well with file argument we are wishing for a new paradigm of saving figures in a simple way, unlike png dev.off() in base R or ggsave() in ggplot2, though latter may also seems simple as well. Multiplot supporting, the current problem, may be an outstanding feature with interesting way to save figures in your plot-constructing workflow, which distincts the package from others… 🤔

[zeileis]

I would also lean towards documenting the limitations. But maybe that's not surprising given that I was rather skeptical of the feature in the first place #125 (comment)

Having said that, hold would be just one more parameter to add and the necessary code modification would likely be minimal as well, right? The if condition for dev.off() would just have to become !is.null(file) && !hold and analogously if !hold no new device should be opened.

Nevertheless, I would be concerned that this just leads to even more parameters that are needed later on... My 2 cents.