| | 1 | == 2013-04-08 == |
| | 2 | |
| | 3 | The new proposed algorithm for the initial ppStack FWHM cuts uses a Gaussian mixture model analysis to attempt to determine the best separation between a possible two component distribution. |
| | 4 | * If Punimodal > 0.5 (this distribution is best described by a single Gaussian mode); limit = MAX(FWHM_i) |
| | 5 | * Otherwise, assume two Gaussians best describe it |
| | 6 | * If pi1 > pi2 (the smaller FWHM group has the majority of the samples); limit = m1 + k * sigma1 |
| | 7 | * If pi2 > pi1 (the larger FWHM group has the majority of the samples); limit = m2 + k * sigma2 |
| | 8 | * If abs(pi1 - pi2) < separation threshold (taken as ~0.2. assume this is nearly unimodal); limit = m2 + k * sigma2 |
| | 9 | * If N <= 4; limit = MAX(FWHM_i) |
| | 10 | * If limit > high_threshold; limit = high_threshold |
| | 11 | * If limit < low_threshold; limit = low_threshold |
| | 12 | |
| | 13 | The results of this algorithm change are shows below, displaying the prior results along with this proposed change. The first figure shows the fraction of input images accepted into the stack for each filter (g,r,i,z,y). The second shows the distribution of the FWHM limits. |
| | 14 | |
| | 15 | [[Image(fractions.png)]] |
| | 16 | |
| | 17 | [[Image(limits.png)]] |
