Question

I’m currently creating my figures in matlab to embed themvia latex into a pdf for later printing. I save the figures and save them via the script export_fig! Now I wonder which is the best way to go:

• Which size of the matlab figure window to chose
• Which -m option to take for the script? It will change the resolution and the size of the image…

I’m wondering about those points in regards to the following two points:

1. When chosing the figure-size bigger, there are more tickmarks shown and the single point markers are better visible
2. When using a small figure and using a big -m option, I still have only some tickmarks
3. When I generate a image which is quite huge (e.g. resolution 300 and still 2000*2000px) and than embed it into the document: Does this than look ugly? Will this be embedded in a nice scaling mode or is it the same ugliness as if you upload a 1000*1000px image onto a homepage and embed it via the widht and height tags in html -> the browser displays it quite ugly because the browser doesn’t do a real resize. So it looks unsharp and ugly.

Thanks in advance!

Answer 1

The MATLAB plots are internally described as vector graphics, and PDF files are also described using vector graphics. Rendering the plot to a raster format is a bad idea, because you end up having to choose resolution and end up with bigger files.

Just save the plot to EPS format, which can be directly embedded into a PDF file using latex. I usually save my MATLAB plots for publication using:

saveas(gcf, 'plot.eps', 'epsc');

and embed them directly into my latex file using:

\includegraphics[width=0.7\linewidth]{plot.eps}

Then, you only need to choose the proportion of the line the image is to take (in this case, 70%).

Edit: IrfanView and others (XnView) don’t display EPS very well. You can open them in Adobe Illustrator to get a better preview of what it looks like. I always insert my plots this way and they always look exactly the same in the PDF as in MATLAB.

One bonus you also get with EPS is that you can actually specify a font size so that the text is readable even when you resize the image in the document.

As for the number of ticks, you can look at the axes properties in the MATLAB documentation. In particular, the XTick and YTick properties are very useful manually controlling how many ticks appear no matter what the window resolution is.

Edit (again): If you render the image to a raster format (such as PNG), it is preferable to choose the exact same resolution as the one used in the document. Rendering a large image (by using a big window size) and making it small in the PDF will yield bad results mainly because the size of the text will scale directly with the size of the image. Rendering a small image will obviously make for a very bad effect because of stretching.

That is why you should use a vector image format. However, the default MATLAB settings for figures produce some of the same problems as raster images: text size is not specified as a font size and the number of ticks varies with the window size.

To produce optimal plots in the final render, follow the given steps:

1. Set the figure’s font size to a decent setting (e.g. 11pt)
2. Render the plot
3. Decide on number of ticks to get a good effect and set the ticks manually
4. Render the image to color EPS

In MATLAB code, this should look somewhat like the following:

function [] = nice_figure ( render )
    %
      % invisible figure, good for batch renders.
    f = figure('Visible', 'Off');
      % make plots look nice in output PDF.
    set(f, ...
        'DefaultAxesFontSize', 11, ...
        'DefaultAxesLineWidth', 0.7, ...
        'DefaultLineLineWidth', 0.8, ...
        'DefaultPatchLineWidth', 0.7);
      % actual plot to render.
    a = axes('Parent', f);
      % show whatever it is we need to show.
    render(a);
      % save file.
    saveas(f, 'plot.eps', 'epsc');
      % collect garbarge.
    close(f);
end

Then, you can draw some fancy plot using:

function [] = some_line_plot ( a )
    %
      % render data.
    x = -3 : 0.001 : +3;
    y = expm1(x) - x - x.^2;
    plot(a, x, y, 'g:');
    title('f(x)=e^x-1-x-x^2');
    xlabel('x');
    ylabel('f(x)');
      % force use of 'n' ticks.
    n = 5;
    xlimit = get(a, 'XLim');
    ylimit = get(a, 'YLim');
    xticks = linspace(xlimit(1), xlimit(2), n);
    yticks = linspace(ylimit(1), ylimit(2), n);
    set(a, 'XTick', xticks);
    set(a, 'YTick', yticks);
end

And render the final output using:

nice_figure(@some_line_plot);

With such code, you don’t need to worry about the window size at all. Notice that I haven’t even showed the window for you to play with its size. Using this code, I always get beautiful output and small EPS and PDF file sizes (much smaller than when using PNG).

The only thing this solution does not address is adding more ticks when the plot is made larger in the latex code, but that can’t be done anyways.