Scanning Technically

SCAN - Q: Why didn't may scan pick this up days sooner?


I have a simple section of a more complicated scan that doesn't seem to be working properly and I'm not sure if there is an error in the logic or am I missing something ?

The simple part of my scan is looking for the SMA 5 close crossing above the SMA 10 close.

[type = Stock]
and [SMA(5,close) X  SMA(10, close)]

I usually run this scan after the close each day and it did pick up several stocks on May 27, but when I look at the charts I don't know why it didn't pick them up days earlier on May 23.  Is this an error or am I missing something, here is a close up of a few of the charts and a zoomed in version of a few days before May 27  which clearly shows it crossed on May 23.

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Developing a Scan; Define Your Universe....

The first few lines define your development scan universe and these are mostly primary database variables.  The scan base is basically; Open, High, Low, Close & Vol, everything else has to be calculated.  So it helps the scanning speed and reduces the server load by using primary data first to limit the number of heavy calculations.


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Why Do My "After the Close" Scan Results Change?

Q: Why do I get different results when I run a scan at the close, a few minutes later and then a few hours later.  The scan criteria is the same and the mathematical formulas are the same.  How can the timing of my after the close scan change the math and give me different results ?

A:  Very good question, it doesn't happen often but if you run alot of scans you will occasionally come across this situation.  There are multiple reasons for this, lets look at some of the common causes.  Note this is only a general overview of the basics.

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Writing a Scan, How Does "YOUR" Mind Think?

Have you ever read the scanning documentation or reviewed someone else's scan coding and thought this  just doesn't make sense to me, well you are not alone it happens to all of us.  We are not identical computers running the same version of software, we are individual, (and thats a good thing).

Scans are mathematical relationships between various variables and by default we all think of those relationships a little differently.  Here's a few examples to get you thinking outside of "YOUR" box.

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Scanning to Find Stocks with Selling Climaxes

A selling climax occurs when a stock falls sharply on extremely high volume. As the name infers, a selling climax suggests that selling pressure has peaked and traders should expect some sort of rebound. Think of this selling pressure as a stretched rubber band, which cannot stretch forever. At some point, the rubber band either breaks or snaps back. In chart terms, a rubber band break would be the equivalent of a complete meltdown in prices. A snap back implies an oversold bounce that retraces a portion of the prior decline.

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What's Wrong with this Bearish MACD Crossover scan?


I inserted a predefined scan in the advanced scan workbench for a "Bearish MACD Crossover", however I'm not sure it's right.  I just cleared out all the default criteria and then selected and inserted the predefined Bearish MACD Crossover.  Here is the actual coding.

Scan code

 The coding seems to make sense until the last line which I think may contain some typos.  I understand there is a numerical relationship between signal and line, but what is the relationship between signal and histogram?  Also could someone explain what *0.25 means in the last line…  thanks.

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How can I see exactly what a predefined scan is doing and can I modify it?

 Well the short answer is yes, if you have an Extra level subscription or higher.  Basic or Free members can only review the output list of predefined scans.

 In the Standard Scan workbench there are two ways to add a predefined scan.

 1 - Under the "Global Filters" section just select the predefined scan in the drop down box.  This will add only the filter title, it does not show you the coding details and does not allow modifications.


2 - Under the "Additional Technical Expressions" section, select and insert the scan.  This is the method you want in order to see the coding details and allows you to modify them.

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Modify, Develop and Test a Custom Scan

Some of you might recognize this example from a CSTA webinar I did last Dec, but I thought it was a good time to update and share it with all StockCharts users.  The example starts with a simple predefined scan and shows how it can be modified, step by step.

(Note the techniques described use the advanced scan interface for writing custom scans, thus you will require at least an Extra level membership to create these scans).

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Is It Possible to Change the Default Scan Definitions?


Right now, whenever I open up the Advanced Scan Workbench, I get this default benchmark definition for the universe of securities to scan:

[type = stock] and [daily sma(20,daily volume) > 40000]

This is hopelessly broad in that it includes boatloads of thinly traded stocks, penny stocks, foreign stocks and the like — securities I would never trade in, myself. I have my own definition of a securities universe, which looks like this:

[type = stock] and [[exchange is NYSE] or [exchange is AMEX] or
[exchange is NASDAQ]] and [daily sma(50,daily volume) > 200000] and [Close > 10]

This is my personal universe, and it works for me, but the point is, I would like to change the default securities universe to be that, rather than forcing me to manually change the overly broad universe that's already baked in, every time I log in.

Is there a way to make that change?



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How to Use the Elder Impulse System to Trade


To experienced users of the Elder Impulse system for trading: What parameters for entering and exiting a trade have you found most useful using this system. For example do you exit a trade immediately when the daily 13 day ema chart shows a change from a green price flag to a blue, or do you wait until a red price flag is generated or what?



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