How to use MathPow function

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Hi, I am happy if you can tell me about exponent.

Value = 2^3 = 2x2x2=8

Below is the code

double Value = MathPow(2.0,3.0);


But I want to know below.

How can I know x=3  with mql4 code ?


 
Hong Ling Mu:

Hi, I am happy if you can tell me about exponent.

Value = 2^3 = 2x2x2=8

Below is the code


But I want to know below.

How can I know x=3  with mql4 code ?


https://www.mql5.com/en/docs/standardlibrary/mathematics/stat/mathsubfunctions/statmathlog
 
Using simple math conversion:

log of both side:
log(8) = log(2^X)

simplified to:
log(8) = X * log(2)

thus final result is
X = log(8) / log(2) = 3

in MQL, you can use both MathLog() or MathLog10()

void OnStart()
  {
//---
      PrintFormat("%f", MathLog(8)/MathLog(2));
      PrintFormat("%f", MathLog10(8)/MathLog10(2));
  }
  
   double Value = MathPow(2.0,3.0);
   double root  = MathPow(Value,1/3.0);
   PrintFormat("2^3=%f %f^3=8", Value, root); // 2^3=8.000000 2.000000^3=8
 
Soewono Effendi #:
Using simple math conversion:

log of both side:
log(8) = log(2^X)

simplified to:
log(8) = X * log(2)

thus final result is
X = log(8) / log(2) = 3

in MQL, you can use both MathLog() or MathLog10()

Wow! Simple method.  Thank you so much.
 
William Roeder #:

Hi, Roeder

Can I ask ?

If I use NormailzeDouble and print it.

Why printed value is not sometimes normalize?


double a=4.33456
NormalizeDouble(a,1);
Print(a)

OUTPUT is not 4.
 
Hong Ling Mu #: If I use NormailzeDouble and print it.

You used NormalizeDouble, It's use is usually wrong, as it is in your case.

  1. Floating point has an infinite number of decimals, it's you were not understanding floating point and that some numbers can't be represented exactly. (like 1/10.)
              Double-precision floating-point format - Wikipedia, the free encyclopedia

    See also The == operand. - MQL4 programming forum (2013)

  2. Print out your values to the precision you want with DoubleToString - Conversion Functions - MQL4 Reference.

  3. SL/TP (stops) need to be normalized to tick size (not Point) — code fails on non-currencies.
              On 5Digit Broker Stops are only allowed to be placed on full pip values. How to find out in mql? - MQL4 programming forum (2011)

    And abide by the limits Requirements and Limitations in Making Trades - Appendixes - MQL4 Tutorial and that requires understanding floating point equality Can price != price ? - MQL4 programming forum (2012)

  4. Open price for pending orders need to be adjusted. On Currencies, Point == TickSize, so you will get the same answer, but it won't work on non-currencies. So do it right.
              Trailing Bar Entry EA - MQL4 programming forum (2013)
              Bid/Ask: (No Need) to use NormalizeDouble in OrderSend - MQL4 programming forum (2012)

  5. Lot size must also be adjusted to a multiple of LotStep and check against min and max. If that is not a power of 1/10 then NormalizeDouble is wrong. Do it right.
              (MT4 2013)) (MT5 2022))

  6. MathRound() and NormalizeDouble() are rounding in a different way. Make it explicit.
              MT4:NormalizeDouble - MQL5 programming forum (2017)
              How to Normalize - Expert Advisors and Automated Trading - MQL5 programming forum (2017)

  7. Prices you get from the terminal are already correct (normalized).

  8. PIP, Point, or Tick are all different in general.
              What is a TICK? - MQL4 programming forum (2014)

 
William Roeder #:

You used NormalizeDouble, It's use is usually wrong, as it is in your case.

  1. Floating point has an infinite number of decimals, it's you were not understanding floating point and that some numbers can't be represented exactly. (like 1/10.)
              Double-precision floating-point format - Wikipedia, the free encyclopedia

    See also The == operand. - MQL4 programming forum (2013)

  2. Print out your values to the precision you want with DoubleToString - Conversion Functions - MQL4 Reference.

  3. SL/TP (stops) need to be normalized to tick size (not Point) — code fails on non-currencies.
              On 5Digit Broker Stops are only allowed to be placed on full pip values. How to find out in mql? - MQL4 programming forum (2011)

    And abide by the limits Requirements and Limitations in Making Trades - Appendixes - MQL4 Tutorial and that requires understanding floating point equality Can price != price ? - MQL4 programming forum (2012)

  4. Open price for pending orders need to be adjusted. On Currencies, Point == TickSize, so you will get the same answer, but it won't work on non-currencies. So do it right.
              Trailing Bar Entry EA - MQL4 programming forum (2013)
              Bid/Ask: (No Need) to use NormalizeDouble in OrderSend - MQL4 programming forum (2012)

  5. Lot size must also be adjusted to a multiple of LotStep and check against min and max. If that is not a power of 1/10 then NormalizeDouble is wrong. Do it right.
              (MT4 2013)) (MT5 2022))

  6. MathRound() and NormalizeDouble() are rounding in a different way. Make it explicit.
              MT4:NormalizeDouble - MQL5 programming forum (2017)
              How to Normalize - Expert Advisors and Automated Trading - MQL5 programming forum (2017)

  7. Prices you get from the terminal are already correct (normalized).

  8. PIP, Point, or Tick are all different in general.
              What is a TICK? - MQL4 programming forum (2014)

Thank you so much, I want to check it one by one.
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