This is a bit of a workaround, but it's the only way I know of to export an Excel plot into a vector format such as EPS or EMF. In my case I needed to export the plot to EPS for inclusion within a LaTeX document.
- Create the plot in Excel
- Copy the plot and paste it into a new, empty word document.
- Save the word document as a PDF. When word exports to PDF it embeds the plot in vector form.
- Using Inkscape, import the PDF
- In Inkscape, File -> Document Properties -> Resize page to content… -> Resize page to drawing or selection
- File -> Save as ->
- Select the format you want, SVG, PS, EPS, etc.
And there you have it, publication quality plots from Excel.
Keep in mind that your data values may be extracted through the vector image by someone doing a similar process with your image, i.e., opening it in Inkscape and pulling data points out. It's even worse when you send a plot in a word document; you can often recover the original Excel sheet, including your calculations (not just data!)