PERSIST

[sadyrbek]

dear support,

I set the mychannel history to 200, and PERSIST 1000000.

On the graph, I can see only 200 datas, others are cleared.

But, when I use mychannel[1000], I can see that it stored more than 1000 datas to hard disk.

How can I use these datas on the graphs?

It was recommended on the documentation that decreasind the history and increasing Persist value.

regards,

[AzeoTech]

As it says in the docs, you can only access data past the History limit and into Persist by subsetting. So in a graph, you have to subset, you can just put "myChannel". The best way to do this is an expression like this:

myChannel[bottomAxis.CurrentScaleFrom,BottomAxis.CurrentScaleTo]

The variables inside the [] are the current X axis scaling, so this basically gets all the data that should be displayed.

[Robyn]

I have used this method of displaying the traces into the persist region, without it the data only shows back to the limits of the history. I have histor 3600 points and persist 100,000 on each point and for the time scale I am using this is adequate.

 

On the graph properties/Axes/Bottom Axis i set the time witdth tick and then 14 days in seconds, which is about my 3600 points. However I can not get the charts to show from the current time when I pull them up. I have to pan up to the current time and date, then they seem to stay OK for a while then when I display them they start at a date about a month ago.

 

When I use the Autoscale function by right clicking on the graph, autoscale X autoscales to some period of over ten years instead of the roughly two years my persist data should cover. This makes autoscale pretty useless.

 

Am I missing something? Everything works ok if my history points are 100,000 (I think) but most of the time I am really only interested in seeing the latest 3600 points and allowing the user to pan back through persist if they want.

 

Thanks for your help

 

 

[Robyn]

Thought I had posted a question on this but no answer so I will try again.

I have history 3600 and persist 100,000 for my points, works OK except I am having problems in the charts. I do use myChannel[bottomAxis.CurrentScaleFrom,BottomAxis.CurrentScaleTo] but find that when they are first displayed they do not show the trace from the latest data but rather something back farther, maybe at the end of the 3600 points? This means the user has to always pan forward to see the latest data. Have you seen this and is there a fix

What should the Autoscale From setting be?

Thanks

[AzeoTech]

If you are using Time Width, it should not matter.  However, if you are giving your user's the ability to scroll, you might consider using two variables instead of time width.  I usually like to use one variable for the most recent time, and another for the width in seconds of the x axis.  Then the scale To becomes something like:

 

maxXScale

 

and Scale From becomes:

 

maxXScale - xScaleWidth

 

You can make the graph scroll the latest data by going to the Event for one of the channels being trended and put:

 

if (scrollMyGraph)

   maxXScale = myChannel.time[0]

endif

 

where scrollmygraph is another variable to determine if you are panning or want it to scroll automatically.