diff options
Diffstat (limited to 'web/api/queries/stddev')
| -rw-r--r-- | web/api/queries/stddev/Makefile.am | 8 | ||||
| -rw-r--r-- | web/api/queries/stddev/README.md | 97 | ||||
| -rw-r--r-- | web/api/queries/stddev/stddev.c | 61 | ||||
| -rw-r--r-- | web/api/queries/stddev/stddev.h | 120 |
4 files changed, 0 insertions, 286 deletions
diff --git a/web/api/queries/stddev/Makefile.am b/web/api/queries/stddev/Makefile.am deleted file mode 100644 index 161784b8f..000000000 --- a/web/api/queries/stddev/Makefile.am +++ /dev/null @@ -1,8 +0,0 @@ -# SPDX-License-Identifier: GPL-3.0-or-later - -AUTOMAKE_OPTIONS = subdir-objects -MAINTAINERCLEANFILES = $(srcdir)/Makefile.in - -dist_noinst_DATA = \ - README.md \ - $(NULL) diff --git a/web/api/queries/stddev/README.md b/web/api/queries/stddev/README.md deleted file mode 100644 index 3f751a6e1..000000000 --- a/web/api/queries/stddev/README.md +++ /dev/null @@ -1,97 +0,0 @@ -<!-- -title: "standard deviation (`stddev`)" -sidebar_label: "standard deviation (`stddev`)" -custom_edit_url: https://github.com/netdata/netdata/edit/master/web/api/queries/stddev/README.md -learn_status: "Published" -learn_topic_type: "References" -learn_rel_path: "Developers/Web/Api/Queries" ---> - -# standard deviation (`stddev`) - -The standard deviation is a measure that is used to quantify the amount of variation or dispersion -of a set of data values. - -A low standard deviation indicates that the data points tend to be close to the mean (also called the -expected value) of the set, while a high standard deviation indicates that the data points are spread -out over a wider range of values. - -## how to use - -Use it in alerts like this: - -``` - alarm: my_alert - on: my_chart -lookup: stddev -1m unaligned of my_dimension - warn: $this > 1000 -``` - -`stdev` does not change the units. For example, if the chart units is `requests/sec`, the standard -deviation will be again expressed in the same units. - -It can also be used in APIs and badges as `&group=stddev` in the URL. - -## Examples - -Examining last 1 minute `successful` web server responses: - --  --  --  --  - -## References - -Check <https://en.wikipedia.org/wiki/Standard_deviation>. - ---- - -# Coefficient of variation (`cv`) - -> This query is also available as `rsd`. - -The coefficient of variation (`cv`), also known as relative standard deviation (`rsd`), -is a standardized measure of dispersion of a probability distribution or frequency distribution. - -It is defined as the ratio of the **standard deviation** to the **mean**. - -In simple terms, it gives the percentage of change. So, if the average value of a metric is 1000 -and its standard deviation is 100 (meaning that it variates from 900 to 1100), then `cv` is 10%. - -This is an easy way to check the % variation, without using absolute values. - -For example, you may trigger an alert if your web server requests/sec `cv` is above 20 (`%`) -over the last minute. So if your web server was serving 1000 reqs/sec over the last minute, -it will trigger the alert if had spikes below 800/sec or above 1200/sec. - -## how to use - -Use it in alerts like this: - -``` - alarm: my_alert - on: my_chart -lookup: cv -1m unaligned of my_dimension - units: % - warn: $this > 20 -``` - -The units reported by `cv` is always `%`. - -It can also be used in APIs and badges as `&group=cv` in the URL. - -## Examples - -Examining last 1 minute `successful` web server responses: - --  --  --  --  - -## References - -Check <https://en.wikipedia.org/wiki/Coefficient_of_variation>. - - diff --git a/web/api/queries/stddev/stddev.c b/web/api/queries/stddev/stddev.c deleted file mode 100644 index 8f5431194..000000000 --- a/web/api/queries/stddev/stddev.c +++ /dev/null @@ -1,61 +0,0 @@ -// SPDX-License-Identifier: GPL-3.0-or-later - -#include "stddev.h" - - -// ---------------------------------------------------------------------------- -// stddev - -/* - * Mean = average - * -NETDATA_DOUBLE grouping_flush_mean(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) { - struct grouping_stddev *g = (struct grouping_stddev *)r->grouping.grouping_data; - - NETDATA_DOUBLE value; - - if(unlikely(!g->count)) { - value = 0.0; - *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY; - } - else { - value = mean(g); - - if(!isnormal(value)) { - value = 0.0; - *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY; - } - } - - grouping_reset_stddev(r); - - return value; -} - */ - -/* - * It is not advised to use this version of variance directly - * -NETDATA_DOUBLE grouping_flush_variance(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) { - struct grouping_stddev *g = (struct grouping_stddev *)r->grouping.grouping_data; - - NETDATA_DOUBLE value; - - if(unlikely(!g->count)) { - value = 0.0; - *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY; - } - else { - value = variance(g); - - if(!isnormal(value)) { - value = 0.0; - *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY; - } - } - - grouping_reset_stddev(r); - - return value; -} -*/
\ No newline at end of file diff --git a/web/api/queries/stddev/stddev.h b/web/api/queries/stddev/stddev.h deleted file mode 100644 index f7a1a06c3..000000000 --- a/web/api/queries/stddev/stddev.h +++ /dev/null @@ -1,120 +0,0 @@ -// SPDX-License-Identifier: GPL-3.0-or-later - -#ifndef NETDATA_API_QUERIES_STDDEV_H -#define NETDATA_API_QUERIES_STDDEV_H - -#include "../query.h" -#include "../rrdr.h" - -// this implementation comes from: -// https://www.johndcook.com/blog/standard_deviation/ - -struct tg_stddev { - long count; - NETDATA_DOUBLE m_oldM, m_newM, m_oldS, m_newS; -}; - -static inline void tg_stddev_create(RRDR *r, const char *options __maybe_unused) { - r->time_grouping.data = onewayalloc_callocz(r->internal.owa, 1, sizeof(struct tg_stddev)); -} - -// resets when switches dimensions -// so, clear everything to restart -static inline void tg_stddev_reset(RRDR *r) { - struct tg_stddev *g = (struct tg_stddev *)r->time_grouping.data; - g->count = 0; -} - -static inline void tg_stddev_free(RRDR *r) { - onewayalloc_freez(r->internal.owa, r->time_grouping.data); - r->time_grouping.data = NULL; -} - -static inline void tg_stddev_add(RRDR *r, NETDATA_DOUBLE value) { - struct tg_stddev *g = (struct tg_stddev *)r->time_grouping.data; - - g->count++; - - // See Knuth TAOCP vol 2, 3rd edition, page 232 - if (g->count == 1) { - g->m_oldM = g->m_newM = value; - g->m_oldS = 0.0; - } - else { - g->m_newM = g->m_oldM + (value - g->m_oldM) / g->count; - g->m_newS = g->m_oldS + (value - g->m_oldM) * (value - g->m_newM); - - // set up for next iteration - g->m_oldM = g->m_newM; - g->m_oldS = g->m_newS; - } -} - -static inline NETDATA_DOUBLE tg_stddev_mean(struct tg_stddev *g) { - return (g->count > 0) ? g->m_newM : 0.0; -} - -static inline NETDATA_DOUBLE tg_stddev_variance(struct tg_stddev *g) { - return ( (g->count > 1) ? g->m_newS/(NETDATA_DOUBLE)(g->count - 1) : 0.0 ); -} -static inline NETDATA_DOUBLE tg_stddev_stddev(struct tg_stddev *g) { - return sqrtndd(tg_stddev_variance(g)); -} - -static inline NETDATA_DOUBLE tg_stddev_flush(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) { - struct tg_stddev *g = (struct tg_stddev *)r->time_grouping.data; - - NETDATA_DOUBLE value; - - if(likely(g->count > 1)) { - value = tg_stddev_stddev(g); - - if(!netdata_double_isnumber(value)) { - value = 0.0; - *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY; - } - } - else if(g->count == 1) { - value = 0.0; - } - else { - value = 0.0; - *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY; - } - - tg_stddev_reset(r); - - return value; -} - -// https://en.wikipedia.org/wiki/Coefficient_of_variation -static inline NETDATA_DOUBLE tg_stddev_coefficient_of_variation_flush(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) { - struct tg_stddev *g = (struct tg_stddev *)r->time_grouping.data; - - NETDATA_DOUBLE value; - - if(likely(g->count > 1)) { - NETDATA_DOUBLE m = tg_stddev_mean(g); - value = 100.0 * tg_stddev_stddev(g) / ((m < 0)? -m : m); - - if(unlikely(!netdata_double_isnumber(value))) { - value = 0.0; - *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY; - } - } - else if(g->count == 1) { - // one value collected - value = 0.0; - } - else { - // no values collected - value = 0.0; - *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY; - } - - tg_stddev_reset(r); - - return value; -} - -#endif //NETDATA_API_QUERIES_STDDEV_H |