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plot.xts: automatic ylim fails #156

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DanVal80 opened this issue Oct 19, 2016 · 0 comments
Closed

plot.xts: automatic ylim fails #156

DanVal80 opened this issue Oct 19, 2016 · 0 comments
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@joshuaulrich
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bug plot
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Release 0.10-1

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@DanVal80
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plot.xts seems to have an issue at determining the ylim range when a timeseries has constant value for its entire duration.

Here is a reproducible example:

data=rep(100, 23); #23 observation with value 100
index=seq(as.POSIXlt("2016-06-01 01:00"), as.POSIXlt("2016-06-01 23:00"), by="60 min"); # 23 timestamps spaced hourly
data.xts<-xts(data,index);
plot(data.xts);

which results in:

Error in segments(xlim[1], y_grid_lines(get_ylim()[[2]]), xlim[2], y_grid_lines(get_ylim()[[2]]), :
cannot mix zero-length and non-zero-length coordinates

Setting the ylim manually with plot(data.xts, ylim=c(0,110)) prevents the error from happening.
I am using the last xts version from git-hub (cloned last week).
joshuaulrich added a commit that referenced this issue Jul 13, 2017
@joshuaulrich
Create ylim when series is constant
820a62a 
plot.xts() would error if called on an object with a series of one
constant value (e.g. .xts(rep(1,10), 1:10)) because the y-coordinates
are the same.

Create different y-coordinates that are +/-20% from the series value.

Also move the check for all ylim equal to zero outside of the if/else
block. This avoids code duplication, and therefore potential future
bugs.

Fixes #156.
@joshuaulrich joshuaulrich self-assigned this Jul 13, 2017
@joshuaulrich joshuaulrich added this to the Release 0.10-1 milestone Jul 29, 2017
@joshuaulrich joshuaulrich mentioned this issue Aug 16, 2017
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bollard added a commit to bollard/xts that referenced this issue May 27, 2022
@bollard
Check for constant ylim susceptible to numerical precision issues
07de4c7 
I am attempting to use `plot.xts` to plot a series which contains constant values, however I encounter the error

> Error in segments(xlim[1], y_grid_lines(get_ylim()[[2]]), xlim[2], y_grid_lines(get_ylim()[[2]]), :
> cannot mix zero-length and non-zero-length coordinates

After a little Googling, I was puzzled to see that this issue was fixed in joshuaulrich#156

With the help of `debug` I found that in my case, numerical precision issues we're causing my data to side step the check. The difference can only be seen with `sprintf`. Debug console output

```
Debug> yrange <- range(cs$Env$xdata[, 1][subset], na.rm = TRUE)
Debug> dput(yrange)
c(6e+05, 6e+05)
Debug> yrange[1L] == yrange[2L]
[1] FALSE
Debug> sprintf("%.6f", yrange[[1]])
[1] "600000.000000"
Debug> sprintf("%.9f", yrange[[1]])
[1] "600000.000000000"
Debug> sprintf("%.12f", yrange[[1]])
[1] "599999.999999999767"
Debug> sprintf("%.12f", yrange[[2]])
[1] "600000.000000000116"
Debug> isTRUE(all.equal(yrange[1], yrange[2]))
[1] TRUE
```

Proposal is to replace the strict `==` check, with `all.equal`, which includes a tolerance of `tolerance=sqrt(.Machine$double.eps)`

Thanks
@bollard bollard mentioned this issue May 27, 2022
Merged
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