I am using a Mac Mini (Late 2012) that is running mac OS 10.9.5 (Mavericks).
I avoided upgrading to mac OS 10.10 (Yosemite) when it was first released because of all of the stability issues surrounding it and have stuck to mac OS 10.9.5.
The only way to get an older OS directly from Apple is to have previously 'purchased it' - even if it was free - then it will appear in your purchase history in the App Store.
If it's not in your purchase history, then you'll have to get it from a trustworthy friend [or less-trustworthy torrent etc] 10.10.
Note: I originally failed to notice the System Requirements link, so this answer has been changed from a previous incorrect one.
This directory contains binaries for a base distribution and packages to run on Mac OS X (release 10.6 and above).
I would like to avoid mac OS 10.11 (El Capitan) for a while if possible.
Now that mac OS 10.11 (El Capitan) has been released, what can I do to upgrade to mac OS 10.10.5 if/when I wish to?As of 2016/03/01 package binaries for R versions older than 2.12.0 are only available from the CRAN archive so users of such versions should adjust the CRAN mirror setting accordingly.Important: since R 3.4.0 release we are now providing binaries for OS X 10.11 (El Capitan) and higher using non-Apple toolkit to provide support for Open MP and C 17 standard features. Please check the MD5 checksum of the downloaded image to ensure that it has not been tampered with or corrupted during the mirroring process.The update pages you link to have small clickable text at the bottom giving System Requirements.These system requirements clarify that the "OS X Yosemite 10.10.5 Update" only works if you have 10.10.4 already installed, and that the "OS X Yosemite 10.10.5 Combo Update" only works if you have some previous version of Yosemite installed, i.e. Neither can be used to upgrade from Mavericks or any other earlier version of OSX.