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home [2019/10/31 10:57]
a.leofreddi
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a.leofreddi [Why?]
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 </​PRELOAD>​ </​PRELOAD>​
 ====== TimEL: Time-series Expression Language ====== ====== TimEL: Time-series Expression Language ======
 +
 +===== TL;DR =====
 +Pick a random example in the <​html><​a href="/​console"​ target="​_blank">​📺 online console</​a></​html>​ and try it yourself!
  
 ===== Why? ===== ===== Why? =====
-Monitoring, ​metering, ​IoT, pay-per-use billing: ​these are only few examples of applications that rely on time-series data! Often you want the final user to be able to manipulate ​and customize some results based on some time-series data - that's when TimEL comes in handy!+Manipulating time-series is a common use case for metering, ​monitoringIoT and pay-per-use billing ​systems. 
 + 
 +You may wonderthere are other time-series ​libraries out there, why TimEL? 
 + 
 +---- 
 + 
 +=== Keep your data: do not resample your time series === 
 + 
 +Many time-series systems automatically upscale your value to a certain interval (let's say a value every 60 seconds): this produces a lot of duplicates ​and also limits granularity:​ what if there is a value change that lasted for less than 60 seconds? The information will be somehow lost, as it will be blended with some other value to accommodate the 60 second boundary constraint. 
 + 
 +TimEL won't force you to do that: it will operate directly using your sample timestamps, regardless of their form (aligned, misaligned, constant interval or variable one) or granularity (anything from years to milliseconds). 
 + 
 +**The granularity of your samples drives the computation,​ not the other way around!** 
 + 
 +---- 
 + 
 +=== Do the right thing: gauges vs integrals (counters) === 
 + 
 +Some time-series data come as a gauge, while some other come as a counter (integral). ​TimEL encodes this information directly within its **typing system**, so you do not have to worry.
  
 +Let's imagine you're summing two integral (counter) values: if they'​re not perfectly aligned, TimEL will automatically interpolate when needed.
 ===== What? ===== ===== What? =====
 TimEL is a Java library to compile and evaluate TimEL expressions. TimEL expressions are written in a user-friendly language that allows time-series manipulation without the need of taking care about upscaling, downscaling or mixing up different time series intervals. TimEL is a Java library to compile and evaluate TimEL expressions. TimEL expressions are written in a user-friendly language that allows time-series manipulation without the need of taking care about upscaling, downscaling or mixing up different time series intervals.
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 If we evaluate this expression for an interval in the same day, let's say 06:​00-18:​00,​ it'll report 0.5 - that is half day. If we evaluate it for more days it will count how many days are contained in the interval. The function uniform here returns an integral, so TimEL knows how to interpolate it properly - that is handled by the interpreter so the user does not need to worry no more about time frames. If we evaluate this expression for an interval in the same day, let's say 06:​00-18:​00,​ it'll report 0.5 - that is half day. If we evaluate it for more days it will count how many days are contained in the interval. The function uniform here returns an integral, so TimEL knows how to interpolate it properly - that is handled by the interpreter so the user does not need to worry no more about time frames.
- 
-**TL;DR?** Pick a random example in the <​html><​a href="/​console"​ target="​_blank">​📺 online console</​a></​html>​ and try it yourself! 
  
 ===== Features ===== ===== Features =====
 With TimEL you can: With TimEL you can:
  
-  * **Mix multiple ​time frames** - for example you can sum daily data with hourly data, or even non-regular data like monthly data;+  * **Mix and preserve time-series with misaligned or different ​time frames** - for example you can sum daily data with hourly data, or even non-regular data like monthly data;
   * **Express** easily recurrent quantities, like 10 units every hour;   * **Express** easily recurrent quantities, like 10 units every hour;
   * **Scale** natively integral values (like consumptions) and averages;   * **Scale** natively integral values (like consumptions) and averages;
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