[R] x tick labels - sparse?

[Darren Weber]

Hi,

I'm stuck on creating a plot with x tick labels for every Nth tick
mark - how is that done?  I don't see a simple solution to this in
help(plot) or help(par) and what I've tried is not working, eg, the
following does not work, although it seems intuitive to me that it
should work:

x <- seq(-100,1000,25)
y <- x * x
% find all the x values that are multiples of 100
tmp <- x / 100
tmp <- tmp %% 1
tmp <- tmp > 0
% set all other values to null strings
xtickLabels <- as.character( x )
xtickLabels[tmp] <- ""
plot(x, y, xlab=xtickLabels)


These commands look like this (the plot is not right):

> x <- seq(-100,1000,25)
> x
 [1] -100  -75  -50  -25    0   25   50   75  100  125  150  175  200  225  250
[16]  275  300  325  350  375  400  425  450  475  500  525  550  575  600  625
[31]  650  675  700  725  750  775  800  825  850  875  900  925  950  975 1000
>
> tmp <- x / 100
> tmp
 [1] -1.00 -0.75 -0.50 -0.25  0.00  0.25  0.50  0.75  1.00  1.25  1.50  1.75
[13]  2.00  2.25  2.50  2.75  3.00  3.25  3.50  3.75  4.00  4.25  4.50  4.75
[25]  5.00  5.25  5.50  5.75  6.00  6.25  6.50  6.75  7.00  7.25  7.50  7.75
[37]  8.00  8.25  8.50  8.75  9.00  9.25  9.50  9.75 10.00
>
> tmp <- tmp %% 1
> tmp
 [1] 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50
[16] 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25
[31] 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00
>
> tmp <- tmp > 0
> tmp
 [1] FALSE  TRUE  TRUE  TRUE FALSE  TRUE  TRUE  TRUE FALSE  TRUE  TRUE  TRUE
[13] FALSE  TRUE  TRUE  TRUE FALSE  TRUE  TRUE  TRUE FALSE  TRUE  TRUE  TRUE
[25] FALSE  TRUE  TRUE  TRUE FALSE  TRUE  TRUE  TRUE FALSE  TRUE  TRUE  TRUE
[37] FALSE  TRUE  TRUE  TRUE FALSE  TRUE  TRUE  TRUE FALSE
>
> xtickLabels <- as.character( x )
> xtickLabels
 [1] "-100" "-75"  "-50"  "-25"  "0"    "25"   "50"   "75"   "100"  "125"
[11] "150"  "175"  "200"  "225"  "250"  "275"  "300"  "325"  "350"  "375"
[21] "400"  "425"  "450"  "475"  "500"  "525"  "550"  "575"  "600"  "625"
[31] "650"  "675"  "700"  "725"  "750"  "775"  "800"  "825"  "850"  "875"
[41] "900"  "925"  "950"  "975"  "1000"
>
> xtickLabels[tmp] <- ""
> xtickLabels
 [1] "-100" ""     ""     ""     "0"    ""     ""     ""     "100"  ""
[11] ""     ""     "200"  ""     ""     ""     "300"  ""     ""     ""
[21] "400"  ""     ""     ""     "500"  ""     ""     ""     "600"  ""
[31] ""     ""     "700"  ""     ""     ""     "800"  ""     ""     ""
[41] "900"  ""     ""     ""     "1000"
>
> y <- x * x
> y
 [1]   10000    5625    2500     625       0     625    2500    5625   10000
[10]   15625   22500   30625   40000   50625   62500   75625   90000  105625
[19]  122500  140625  160000  180625  202500  225625  250000  275625  302500
[28]  330625  360000  390625  422500  455625  490000  525625  562500  600625
[37]  640000  680625  722500  765625  810000  855625  902500  950625 1000000
>
> plot(x, y, xlab=xtickLabels)
>


Thanks in advance.

Best, Darren