AB does that automatically by not loading all data, unless required by your calculations.
AB uses Quick AFL, which load a few more bars than visible, but far fewer than available. ----- Original Message ----- From: "cdkylstra" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, September 03, 2007 6:13 PM Subject: [amibroker] No Joy with STATUS output: firstVisibleBarIndex and lastVisibleBarIndex > Hi All, > > I want to obtain the first and last visible bars on the display so > that I can re-calculate the indicators just for that portion of the > data, i.e., only for what is showing. This is an attempt to speed up > the display of results by not re-calculating the indicators for the > entire time series. > > From the forums, STATUS is clearly the right function to use. > > However, I must be missing something, because the values output by > STATUS don't match the index numbers of the first and last visible > bars. In fact, if I don't select a date/bar, yet move the scroll > slider to view different portions of the time series, the output > values remain constant, as if I was still looking at the very end of > the data series. > > (BTY, I am using AB 4.90.5, May 27, 2007; Windows XP SP2. ) > > Here is what I added to my afl chart equations, just before calling > the function with which I want to calculate just the data to display. > > printf("\nStatus Info\n" ); > > printf( "1stVB = " + Status( "firstvisiblebar" ) + "\n" ); > printf( "LstVB = " + Status( "lastvisiblebar" ) + "\n" ); > printf( "1stVBI = " + Status( "firstvisiblebarindex" ) + "\n" ); > printf( "LstVBI = " + Status( "lastvisiblebarindex" ) + "\n" ); > > > Here is typical output in Interpretative Window > > Status Info > 1stVB = 1749 > LstVB = 1926 > 1stVBI = 1749 > LstVBI = 1926 > > 1926 (+1) is the number of bars in the time series, i.e., BarCount == > 1927. > > 1749 seems to be related to the default number of bars displayed, > which is 159, plus 10 blank bars in right margin. However, the > different is 177, or 178 bars (= 1926 - 1749 + 1). I assume this pads > a little on the Left (~18 bars) for indicator startup transients. > > When I first started checking the STATUS output, I had SetBarsRequired > commented out. And the 1st and last visible bars (VB) showed numbers > like 59 and 217 (difference is 159), while the VBI numbers were as > above. Once I used SetBarsRequired, however, it did not matter what > parameters I used or even if I removed SetBarRequired. The VB and VBI > values remained identical, as above. > > If I pulled the scoll bar at the bottom to the left, back in time, the > above values did not change. It was as if I was still looking at the > end of the times series. > > If I selected a bar, the "last" values do change, however, they > changed to the index of the selected bar, not the index of the last > bar on the right side of the display. And the first values changed to > a value 177 less than the last values, even if I selected a bar near > the left side of the display. > > Oh yes, I can zoom in or out and the output values do not change, even > with the doubling or halving of the display. > > > So, I am not getting the literal left and right sides of the display, > even allowing for padding. > > Would appreciate any guidance. > > Chester > > > > > Please note that this group is for discussion between users only. > > To get support from AmiBroker please send an e-mail directly to > SUPPORT {at} amibroker.com > > For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG: > http://www.amibroker.com/devlog/ > > For other support material please check also: > http://www.amibroker.com/support.html > > Yahoo! Groups Links > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
