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Delphi 7 TDBChart

Posted on 2006-07-06
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Last Modified: 2008-01-09
Dear Experts.

I have a database application in Delphi 7.
Am using TDBChart to plot averages from the DB.
I am using a TLineSeries to plot these averages.

Is there a way to eliminate abnormal high spikes on the Chart?
Cause I am analyzing massas of data and maybe on record are way out high which in return
pushes the average up.
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Question by:Marius0188
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11 Comments
 
LVL 11

Expert Comment

by:calinutz
ID: 17053492
Maybe if you do a function for regularizing the results or add conditions to your Query... because the DBChart does not know that it bothers you to have too big values in it. Also you can play with the scaling of the DBChart to increase the maximum on the vertical, that would probabely lead to a smoothing of the chart.

Regards.
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LVL 17

Expert Comment

by:TheRealLoki
ID: 17055085
Personally, I would add a "calculated" field to the query (double click on the TQuery, new field, "calculated")
"Nice_Big_Value"

then add click on the Query component, and add an OnCalcFields event

procedure TForm1.Query1CalcFields(DataSet: TDataSet);
begin
  Dataset.FieldByName('Nice_Big_Value').AsFloat := max(1000, Dataset.FieldByName('NORMAL_Big_Value').AsFloat); // max of 1000
// same as  Query1NiceBigValue.AsFloat := max(1000, Query1Normal_Big_Value.AsFloat);
end;

then in your dbchart, use Nice_Big_Value instead of Big_Value
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LVL 17

Expert Comment

by:TheRealLoki
ID: 17055322
sorry, it should be MIN, not max as in
:= MIN((1000, Dataset.FieldByName('NORMAL_Big_Value').AsFloat);
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LVL 17

Expert Comment

by:TheRealLoki
ID: 17055338
btw, you need to add "math" to your uses clause
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Author Comment

by:Marius0188
ID: 17075145
Thanks for help so far.

When I draw a TLineSeries chart based on averages of thousands of record's data it is very spiky.
I do not want to manipulate the actual data but would rather draw a very smooth line chart.
For example: In stock exchange you get Moving Averages. I need to draw the same smooth line.
Is there a series that can do this or how will I go about doing this?
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Author Comment

by:Marius0188
ID: 17075234
Maybe I am not clear enough.

Instead of the spikes going up and down accross the X axis I would like to draw a smooth line.
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LVL 17

Accepted Solution

by:
TheRealLoki earned 250 total points
ID: 17078267
If you really do just mean "Average"
then add a 2nd series. make this a Function
(click "add series" you choose "function" instead of "series")
make sure you tell it to use "Average" and the "series1" for the data

If you mean a spline curve (curve fitting) ?
Teechart PRO has this by using gaussian polynomials
Delphi ships with standard TeeChart
When you click "add series" you choose "function" instead of "series"
If you do not have teechart pro, I think you can add one yourself (if you know the math)
by using 2 series
1 series you just show the points, and this is your real data
you create the 2nd series by using sin and the 1st series points
Don't ask me how to do the maths though :-)

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Author Comment

by:Marius0188
ID: 17078283
Yes I think what I need is your second explanation.
The curve fitting.
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LVL 17

Expert Comment

by:TheRealLoki
ID: 17078804
there's a teechart pro trial version you can download, but I don't think you'll get this feature for free in teechart any time soon
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Author Comment

by:Marius0188
ID: 17079577
1. Where can I download Teechart Pro Trial?
Do you have an url for me please.

2. Isn't there any other free charting components for Delphi that might assist me?
Please provide urls for download etc...
0
 
LVL 11

Expert Comment

by:calinutz
ID: 17092830
For teechart Pro evaluation check out this link:
http://www.steema.com/downloads/dwn_tch_vcl.html

As for other delphi charting components that are free and also provide lot of functionalities there isn't any. At least none that I know of, and I know I checked a couple of times in all the right places.
Best place I've found is this:
http://www.torry.net/pages.php?id=195

Regards
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