Help in understanding Current Candle +1 vs -1

[michaelb]

I have an indicator that alerts when 2 Moving Averages cross.

This indicator has the following section of code--

limit=Bars-counted_bars;

for(i = 0; i <= limit; i++) {
fasterEMAnow = iMA(NULL, 0, FasterEMA, 0, MODE_EMA, PRICE_CLOSE, i);
fasterEMAprevious = iMA(NULL, 0, FasterEMA, 0, MODE_EMA, PRICE_CLOSE, i+1);
fasterEMAafter = iMA(NULL, 0, FasterEMA, 0, MODE_EMA, PRICE_CLOSE, i-1);

slowerEMAnow = iMA(NULL, 0, SlowerEMA, 0, MODE_EMA, PRICE_CLOSE, i);
slowerEMAprevious = iMA(NULL, 0, SlowerEMA, 0, MODE_EMA, PRICE_CLOSE, i+1);
slowerEMAafter = iMA(NULL, 0, SlowerEMA, 0, MODE_EMA, PRICE_CLOSE, i-1);

The FOR loop begins with i=0

fasterEMAnow is looking at candle [i] which is [0]

fasterEMAprevious is looking at candle [i+1] which is [1]

but fasterEMAafter is looking at candle [i-1] which is [-1] This is the statement I do not understand.

How do these statements determine if a cross occurs?

In addition, the alert only happens on a closed candle, never an open candle.

Any guidance would be appreciated. Thank you.

[[Deleted]]

"I understand that candle [i] is the current candle being formed right now"

not really - since i can be any value from 0..limit

current is relative to where standing.

if speaking relative to Time[] and i=0 then Time[i] is current/rightMost/buildingNow chart period and Time[i+1] is at an historically older 'Time' by one chart bar period in seconds.

if speaking relative to a looping construct then Time[i] is current regards whatever doing inside the loop, keeping in mind that i>0 is going left/older regarding Time.

ok drone over.

.

"but how can you have candle [i-1] ??"

if( i>0 ) Time[i] = the i'th bar historically older/leftwards to [0] and [i-1] is ok as i>0, yes? ie, start decrementing i and you go right towards most recent/current Bar[0]

typically, many use [i=1] as first bar going left in a loop. Why? because it has fully formed and now static O,H,L,C,Time,Volume (NOTE:the Open and Time are static values on the first data tick of a new bar [0])

also, at this first data tick - is when the previous Time[0] is now Time[1] and Time[0] at this first data tick is the [now] static Time for this forming new bar [0] with of course it's own static Open value)

.

"slowerEMAafter = iMA(NULL, 0, SlowerEMA, 0, MODE_EMA, PRICE_CLOSE, i-1);"

no can do IF i=0,1,2,..

see? as if i=0 then [i-1] is equiv to [-1] and that bar not exist/is technically illegal array element access... cuz array storage goes from 0,1,...,n-1 where n is dimension size.

.

ok? or not?

me? now all confused too - lol

.

hth

[Paul]

I think the i-1 is only valid for i>0. Or to look at it another way the indicator is only valid up to the last closed candle where 3 values of i are valid.