Hi Japple,

Without getting into the EST just yet, let's have a look at what you are trying to achieve with your codes.

The first thing to notice is the abundance of PREVs in the code. PREV is a recursive function and is extremely processor intensive and can slow your entire computer to a crawl, so its a really good idea to limit these functions to the absolute minimum required.

In your function you do something like:



As PREV is already 1 (we know this because that's how we ended up in the If() in the first place) then you can save a PREV by replacing the second instance with the first value:



Another point I would suggest is to maximise the use of variables as these will make code debugging and maintenance easier.

My last suggestion is to start logic problems, logically! Your trade latch system starts of by looking to see if we are already in a long trade, but it makes more sense (to me) to start the process with no trades open and go from there. Each has their own personal preferences, but try these ideas out, you might like them?!

As for the latching...

Your "a" variable is already the latch and does not require the use of the external function. As you have discovered for yourself, the generic forum.latch does not do entry price based exits so you are stuck with using PREV based latches or having custom codes written for you.

Correct me if I am wrong, but after rejigging the entire code section, I end up with something more "simple":



The trade latch reads:
{1:} If no trades are open PREV=0, then look for a trade entry. If LE=1 and SE=0, then we go long (LE-SE=1), otherwise, if LE=0 and SE=1 then we go short (LE-SE=-1) otherwise if LE and SE are both zero or both one, then we do nothing and sit aside.
{2:} PREV=1 so we are already in a long trade, so check for the exit condition that swing to the short trade. If this condition is triggered, go short, otherwise stay in the long trade.
{3:} As we have arrived here, PREV is not zero and it is not one, so in our latch which can only have three values, PREV=-1 so we are in a short trade. Check the exit condition that will swing the trade to the long side. If this event is triggered, go long, otherwise stay in the short trade.

To employ this in the EST, just set the entry and exit triggers using codes like:



If this is all correct, then we can turn our attention to the EST and its pricing of trades?


Hope this helps

wabbit [:D]


[edit]
P.S. Roy Larsen wrote a very good tutorial available from http://forum.equis.com/files/3015/metastock_files/entry19675.aspx

Hi Wabbit,

I've been testing your code and trying to reference an external security on which to base the signals using the code below. I keep getting the following error yet I've checked and double-checked and the data is all there. I tried testing both daily and weekly periodicity and get the same result. I then tested a simple mov avg crossover system using the same data settings and all went fine, so I'm guessing the Security() function doesn't like something in your code but I can't figure it out. I couldn't find any reference to this error anywhere in the forum. Any ideas?

Thanks,

Jim

No data exists for requested date range in Security() function. Symbol: "VLE-I" Range: 9/2/1988 to 9/2/1988

{Buy Signal}

d:= opt1 / 100;

CF:= Security("C:\Data\MSDATA\FT\INDEXFAM\VLE-I",Close);

LE:=CF > Lowest(CF)*(1+d);
SE:=CF < Highest(CF)*(1-d);

tr:=
{1:}If(PREV=0, LE-SE,
{2:}If(PREV=1, If(CF<HighestSince(1,PREV<>1,CF)*(1-d),-1,1),
{3:}If(CF>LowestSince(1,PREV<>-1,CF)*(1+d),1,-1)));

{plot in new inner window}
tr<>1;