# Functions for average and variance calulations Classic List Threaded 4 messages Open this post in threaded view
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## Functions for average and variance calulations

 Hi, are there such functions in the FFmpeg library? I have an integer array with lets say 13 numbers (accumulated counts of X in the range of 0..12) like: a) 0 1 0 1 2 7 9 5 4 3 2 0 1 b) 7 1 9 8 1 6 2 0 0 1 9 1 0 In a) the average X would be ~6 and the variance would be small. In b) the average X would be ~3.5 and the variance would be bigger. I'm looking for functions that can calulate such values with a result in float resolution. -Ulf -- Von meinem Seibert gesendet _______________________________________________ ffmpeg-user mailing list [hidden email] https://ffmpeg.org/mailman/listinfo/ffmpeg-userTo unsubscribe, visit link above, or email [hidden email] with subject "unsubscribe".
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## Re: Functions for average and variance calulations

 Am 09.07.19 um 00:25 schrieb Ulf Zibis: > Hi, > > are there such functions in the FFmpeg library? > > I have an integer array with lets say 13 numbers (accumulated counts of > X in the range of 0..12) like: > a) 0 1 0 1 2 7 9 5 4 3 2 0 1 > b) 7 1 9 8 1 6 2 0 0 1 9 1 0 > > In a) the average X would be ~6 and the variance would be small. > In b) the average X would be ~3.5 and the variance would be bigger. > > I'm looking for functions that can calulate such values with a result in > float resolution. > > -Ulf For a qudratic average I could use something like:         float sum = 0;         for (int i = s->span_r -  s->span_l; i >= 0; i--)             sum += pow(counts[i], 2);         float qaverage = sqrt(sum / (s->span_r -  s->span_l + 1)); But for calculating the variance I'm lost. I assume, there are already solutions for both in the FFmpeg lib. -Ulf _______________________________________________ ffmpeg-user mailing list [hidden email] https://ffmpeg.org/mailman/listinfo/ffmpeg-userTo unsubscribe, visit link above, or email [hidden email] with subject "unsubscribe".
 Am 09.07.19 um 10:06 schrieb Paul B Mahol: > On 7/9/19, Ulf Zibis <[hidden email]> wrote: >> Am 09.07.19 um 00:25 schrieb Ulf Zibis: >>> Hi, >>> >>> are there such functions in the FFmpeg library? >>> >>> I have an integer array with lets say 13 numbers (accumulated counts of >>> X in the range of 0..12) like: >>> a) 0 1 0 1 2 7 9 5 4 3 2 0 1 >>> b) 7 1 9 8 1 6 2 0 0 1 9 1 0 >>> >>> In a) the average X would be ~6 and the variance would be small. >>> In b) the average X would be ~3.5 and the variance would be bigger. >>> >>> I'm looking for functions that can calulate such values with a result in >>> float resolution. >>> >>> -Ulf >> For a qudratic average I could use something like: >>         float sum = 0; >>         for (int i = s->span_r -  s->span_l; i >= 0; i--) >>             sum += pow(counts[i], 2); >>         float qaverage = sqrt(sum / (s->span_r -  s->span_l + 1)); >> >> But for calculating the variance I'm lost. I assume, there are already >> solutions for both in the FFmpeg lib. > No, they are not there. At least not freely available via API. > If you have formula for variance then its easy to implement it. I now have developed these functions. Maybe one has interest, so I share them. -Ulf _______________________________________________ ffmpeg-user mailing list [hidden email] https://ffmpeg.org/mailman/listinfo/ffmpeg-userTo unsubscribe, visit link above, or email [hidden email] with subject "unsubscribe". util_statistics_1.patch (7K) Download Attachment