```
#
# PSAR_MTF by @mark.917
#
input accelerationFactor = 0.02;
input accelerationLimit = 0.2;
assert(accelerationFactor > 0, "'acceleration factor' must be positive: " + accelerationFactor);
assert(accelerationLimit >= accelerationFactor, "'acceleration limit' (" + accelerationLimit + ") must be greater than or equal to 'acceleration factor' (" + accelerationFactor + ")");
def state = {default init, long, short};
def extreme;
def SAR;
def acc;
input PSAR_Timeframe = AggregationPeriod.FIFTEEN_MIN;
def high = high(period = PSAR_Timeframe);
def low = low(period = PSAR_Timeframe);
switch (state[1]) {
case init:
state = state.long;
acc = accelerationFactor;
extreme = high;
SAR = low;
case short:
if (SAR[1] < high)
then {
state = state.long;
acc = accelerationFactor;
extreme = high;
SAR = extreme[1];
} else {
state = state.short;
if (low < extreme[1])
then {
acc = min(acc[1] + accelerationFactor, accelerationLimit);
extreme = low;
} else {
acc = acc[1];
extreme = extreme[1];
}
SAR = max(max(high, high[1]), SAR[1] + acc * (extreme - SAR[1]));
}
case long:
if (SAR[1] > low)
then {
state = state.short;
acc = accelerationFactor;
extreme = low;
SAR = extreme[1];
} else {
state = state.long;
if (high > extreme[1])
then {
acc = min(acc[1] + accelerationFactor, accelerationLimit);
extreme = high;
} else {
acc = acc[1];
extreme = extreme[1];
}
SAR = min(min(low, low[1]), SAR[1] + acc * (extreme - SAR[1]));
}
}
plot parSAR = SAR;
parSAR.SetPaintingStrategy(PaintingStrategy.POINTS);
parSAR.SetDefaultColor(GetColor(5));
def signalDown = sar crosses above close;;
def signalUp = sar crosses below close;
def mode = if signalUp then 1 else if signalDown then 0 else mode[1];
plot upArrow = if signalUp then low else double.nan;
plot downArrow = if signalDown then high else double.nan;
upArrow.setPaintingStrategy(PaintingStrategy.ARROW_UP);
downArrow.setPaintingStrategy(PaintingStrategy.ARROW_DOWN);
```