[R-SIG-Finance] chart_Series: Adding multiple custom indicators

[Joshua Ulrich]

On Wed, Jul 5, 2023 at 3:11 PM Mike <mike9 using posteo.nl> wrote:
>
> Some time ago I wrote an R script where I added custom indicators to
> a main chart by putting them into a list like this:
>
> CODE:
> data (sample_matrix, package="xts")
> data <- as.xts (sample_matrix)
>
> ta <- list ()
> ta[[1]] <- "add_TA (SMA (data$Close, 20), col='#BB0000')"
> ta[[2]] <- "add_TA (SMA (data$Close, 3), col='#00BB00')"
>
> co <- chart_Series (data, name='test data', TA=ta)
> plot (co)
>
Thanks for the reproducible example!

>
> After some updates, and now running
> > packageVersion('quantmod')
> [1] '0.4.23'
> I started the code again and got this:
>
> Error in !is.null(TA) && nchar(TA) > 0 :
>   'length = 2' in coercion to 'logical(1)'
>
> I don't get the error when I add one indicator only.
>
> On an older machine running quantmod 0.4.20 I get this message as a
> warning instead of an error.
>
>
> What causes the error and what is the best practice to plot a chart
> (using the new chart_Series) with multiple custom indicators?
>
That chart_Series() code didn't change between those 2 versions of
quantmod. This went from a warning to an error based on changes in R
itself. You can verify by running the code below on both machines:

ta <- list("a", "b")
!is.null(ta) && nchar(ta) > 0
## Error in !is.null(ta) && nchar(ta) > 0 :
##  'length = 2' in coercion to 'logical(1)'

The chart_Series() docs say that the TA arg should be "a character
string of semi-colon seperated TA calls". So you can do this:

chart_Series(data, name = "test data", TA = paste(ta, collapse = ";"))

Best,
Josh


> Mike
>
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-- 
Joshua Ulrich  |  about.me/joshuaulrich
FOSS Trading  |  www.fosstrading.com