Hello Heather - The first thing to do is explore your data and make sure that your grid and points have imported correctly. Different spatial packages have slightly different classes, so its always a good idea to use class() to make sure that your object is what you think it is. plot(), summary() and str() are also often helpful. If you are still unable to get overlay to work, try the "quadratcount" function in the spatstat package (you will need to define your points as a spatial point pattern first). You can specify either the number of pixels you want to divide your study area into, provide 2 vectors of break-points, or format your grid as a "tesselation". The drawback is that with thousands of pixels, it may be quite slow. Try it on a subset of the data first, to see if it does what you want. Others will probably have more efficient suggestions. HTH, Anna ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Dr. Anna E. Marburg Postdoctoral researcher Ecosystem Processes Team Landcare Research P O Box 40 Lincoln 7640 NEW ZEALAND phone + 64 3 321 9729 MarbugA at landcareresearch.co.nz ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Please consider the environment before printing this email Warning: This electronic message together with any attachments is confidential. If you receive it in error: (i) you must not read, use, disclose, copy or retain it; (ii) please contact the sender immediately by reply email and then delete the emails. The views expressed in this email may not be those of Landcare Research New Zealand Limited. http://www.landcareresearch.co.nz
Counting number of points per pixel in a grid
1 message · Anna Marburg