NAME: msrcor PURPOSE: (one line only) Spatial correlation souce positions found in multiple lists DESCRIPTION: This routine is a conceptual extension of the Astronomy Users Library routine, srcor.pro. This extension of this routine is that you can correlate more than two lists of positions. Each call of this routine will serve to add one list to the description of the union of all the prior lists. The lists are copied into the information collected about the set of lists so you don't need to maintain a copy of the original lists. CATEGORY: Photometry CALLING SEQUENCE: msrcor,set,x,y,dcr INPUTS: set - This is the description of the set of all lists seen thus far. There are three ways to signal the first call to this routine. 1) set is undefined 2) set is not a structure 3) set is a valid structure but set.nlists is equal to zero. Note that there is absolutely no performance advantage to maintaining a previous structure and then setting set.nlists=0. If you want to restart it is just as effective to simply say set=0 prior to an initilizing call. If the structure exists already and set.nlists!=0 then the information will be added to and the anonymous structure will be modified before returning. x,y - Array of x and y coordinates for a new list to add to the set. The order in which these array are successively presented to msrcor will determine the ordinal number of the list within the set. dcr - Critical radious outside which correlations are rejected. x,y,dcr can be in any units that make sense to your problem but they must all be the same units. OPTIONAL INPUT PARAMETERS: KEYWORD INPUT PARAMETERS: OUTPUTS: set - Information structure, the following tags are defined: x - X position of source (all lists are concatenated here) y - Y position of source (all lists are concatenated here) objid - vector that matches the length of x and y. These values are unique object id numbers, starting at 0. objcnt - vector that indicates how many times each object appears in the lists (<= nlists) lidx - vector (same length as x,y) that indicates which list the position appears in. nobj - scalar, number of unique objects found. nlists - scalar, total number of lists included. There may be other related information you might like to keep along with this information, such as magnitude or FWHM. If you concatentate everything in list order you will have a vector whose structure matches set.x and set.y and the indexing for all will be the same. KEYWORD OUTPUT PARAMETERS: COMMON BLOCKS: SIDE EFFECTS: RESTRICTIONS: PROCEDURE: MODIFICATION HISTORY: 2008/06/18, Written by Marc W. Buie with algorithmic input from Leslie Young, Southwest Research Institute. 2011/08/02, MWB, promoted all counters and pointers to long, this caused some odd problems when linking a lot of lists.