Hi

I have added a warning (r-devel r72811).

I did this rather than allow vectors for length/angle/code because ...

- consistency with (implicit) description of arguments in help page

- backward compatibility (or at least no risk of not-backwards-incompatible)

- it was easier

Note that it is only the length/angle/code that are scalar, e.g., the

graphical parameters ARE recycled ...

arrows(x0 = x0, y0 = y0, x1 = x1, y1 = y1,

length = mylengths, code = mycodes, angle = myangle,

col = 1:3, lwd=1:3, lty=1:3)

Thanks for the report and suggestion.

Paul

On 20/06/17 09:58, Paul Johnson wrote:

> I was teaching new R users to make some fun graphs. I had some arrows examples

> worked up we came across a problem. The arrows function ignores 2nd

> and following elements of vectors given as code an angle.

>

> Would you please consider 1) allowing vectors for code and angle, or

> 2) returning an error or warning when user mistakenly supplies a

> vector for those parameters? When code like this is wrapped into an

> Sweaved document--we I don't see the graph on the screen--this error

> is difficult to catch while proofreading.

>

> Example:

>

> x0 <- c(-1, -4, 4.5)

> y0 <- c(-1, -4, -8)

> x1 <- c(2, -2, -3)

> y1 <- c(4, 4, 18)

> mylengths <- c(0.2, 0.3, 0.15)

> mycodes <- c(3, 2, 1)

> myangle <- c(10, 60, 80)

>

> plot(x = c(-5, 5), y = c(-10, 20),

> type = "n", xlab = "", ylab = "")

>

> arrows(x0 = x0, y0 = y0, x1 = x1, y1 = y1,

> length = mylengths, code = mycodes, angle = myangle)

>

> I found a workaround, but this is more difficult to explain to beginners...

>

> plot(x = c(-5, 5), y = c(-10, 20),

> type = "n", xlab = "", ylab = "")

>

> mapply(arrows, x0 = x0, y0 = y0, x1 = x1, y1 = y1,

> length = mylengths, angle = myangle, code = mycodes)

>

> pj

>

--

Dr Paul Murrell

Department of Statistics

The University of Auckland

Private Bag 92019

Auckland

New Zealand

64 9 3737599 x85392

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http://www.stat.auckland.ac.nz/~paul/______________________________________________

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