Matlab doesn't change MarkerSize

Hi all,

I know this is a basic one, but for some reason when I plot a figure, certain markers don't change their Size. The code that I use is the following:

plot(datos(index,i+1),headers(1,i+1),'sk','MarkerSize',4,'LineWidth',.25,'MarkerFaceColor',[R G B]);

or

 plot(datos(index,i+1),headers(1,i+1),'pk','MarkerSize',4.5,'LineWidth',.25,'MarkerFaceColor',[R G B]);

When I set the MarkerSize for a square or pentagram shape they always end up in a size 2.9x2.9 (squares) or size 4.2x4.06 (pentagram). I'm saving the figure as a PDF with "print(fig1,saveString,'-dpdf','-fillpage');" don't know if that matters but I thought of mentioning it.

Thanks in advanced,

Carlos TM

[Walter Roberson]

Is the difficulty occurring even on the displayed images, or only in the PDF ?

[Carlos Trasviña]

It's hard to say in the displayed images, but if my sight doesnt fail me I would say that YES, there is a difference in size. In the PDF file I'm sure.

Answer 1

[Greg]

The unit of 'MarkerSize' is 'points' which is typically 1/72 inch. Depending on your OS, there are usually 96 pixels per inch. If you do the math on various marker sizes - and assume that apparent size of a marker is floor of its pixel size - the following sheds a little light:

pts = 4:.1:5;
in = pts./72;
pix = in.*96;
[pts;in;pix]
ans =
  4.0000    4.1000    4.2000    4.3000    4.4000    4.5000    4.6000    4.7000    4.8000    4.9000    5.0000
  0.0556    0.0569    0.0583    0.0597    0.0611    0.0625    0.0639    0.0653    0.0667    0.0681    0.0694
  5.3333    5.4667    5.6000    5.7333    5.8667    6.0000    6.1333    6.2667    6.4000    6.5333    6.6667

This would make me believe that 4.5 looks larger than 4.0-4.4, but it could be a little round-off error in MATLAB's calculation vs. my assumed algorithm above. Try 4.6 for your 'MarkerSize' and see if that helps.

[Greg]

To be really sure, run a range of 'MarkerSize' inputs through a for loop and see where they look bigger:

for ij = 4:.1:5
  figure('Name',sprintf('%.2f',ij));
  plot(1:10,'sk','MarkerSize',ij);
end

[Greg]

Thinking about it more, a ceil as opposed to floor of pixel size would explain it.

[Carlos Trasviña]

I've been running some tests and found out that it seems to be related to the print file format. I tried changing the MarkerSize on different file formats and it did change, although it was never exactly what I was expecting (probably because of the point size).

I think I'll have to make a compromise... in the end, it's mostly aesthetic.

Thanks for your comments!