Solve: "bad guess(es)" error...

[salvomic]

hi,
why this code

Code:


EXPORT provasol()
BEGIN
local yield, coupon, ann, years, price;
coupon:=6.75;
ann:=2;
years:=14;
price:=122.125;
yield := Solve.SOLVE((coupon/ann)*( (1-1/(1+(X/ann))^(ann*years)) / (X/ann) ) + 100/(1+(X/ann))^(ann*years) = price, X);
RETURN yield;
END;

gives error "Bad Guesses"?
If I try with the values in Home I get the correct answer: 0.0459035...

Code:


Solve.SOLVE((6.75/2)*( (1-1/(1+(X/2))^(2*14)) / (X/2) ) + 100/(1+(X/2))^(2*14) = 122.125, X);

Thank you
Salvo

[DrD]

Hi Salvo;

The program's local vars don't persist within the Solve app (out of scope). If you use Globals (see the reserved vars in the code below), the program works fine.

<<A subroutine *could* be used to pass locals to reserved vars, and return the results back to yield, if necessary.>>

Code:


EXPORT provasol()
BEGIN
  local yield, coupon, ann, years, price;

// Using reserved vars as globals
  C:=6.75;
  A:=2;
  Y:=14;
  P:=122.125;

//  Locals don't persist in Solve App
  //coupon:=6.75;
  //ann:=2;
  //years:=14;
  //price:=122.125;

  //yield := Solve.SOLVE((coupon/ann)*( (1-1/(1+(X/ann))^(ann*years)) / (X/ann) ) + 100/(1+(X/ann))^(ann*years) = price, X);
  
  yield := Solve.SOLVE((C/A)*( (1-1/(1+(X/A))^(A*Y)) / (X/A) ) + 100/(1+(X/A))^(A*Y) = P, X);

  RETURN yield;
END;

[salvomic]

(05-31-2015 10:31 AM)DrD Wrote:  Hi Salvo;

The program's local vars don't persist within the Solve app (out of scope). If you use Globals (see the reserved vars in the code below), the program works fine.

<<A subroutine *could* be used to pass locals to reserved vars, and return the results back to yield, if necessary.>>

thank you!
It works.

I'm using it in the first version for my program to calc Bonds (for now, however, this one, with the flag to calculate "financial year" -30/360- gives result for price a little different from the 12C, and sure my formulas aren't correct, and the Prime reset calculating yield for this option: please, try, advice...)

here there are the code:

Code:


EXPORT Bonds()
BEGIN

END;

EXPORT Price()
BEGIN
  local mesg, days1, days2, toReg, N, finAct;
  local sd, sm, sy, md, mm, my, ann;
  local coupon, yi, years, price, inter, dayPer;
  input ({ {sd,[0],{15,15,1}}, 
  {sm,{"1","2","3", "4", "5", "6", "7", "8", "9", "10", "11", "12"}, {40,15,1}}, 
  {sy,[0],{70,20,1}},
  {md,[0],{15,15,2}}, 
  {mm,{"1","2","3", "4", "5", "6", "7", "8", "9", "10", "11", "12"}, {40,15,2}}, 
  {my,[0],{70,20,2}},
  {coupon,[0],{40,15,4}}, {yi,[0], {75,15,4}},
  {ann,[0], {40,15,5}}, {finAct,2,{85,2, 5}}
  }, 
  "Price of Bond (maturity 100)", {"sd", "sm", "sy", "md", "mm", "my", 
  "Coupon", "y%", "ann", "Financial"}, 
  {"Settlement day", "Settlement month", "Settlement year (purchase)", 
  "Maturity day", "Maturity month", "Maturity year (regulation)", 
  "Coupon payment %", "yield %", "n. of annuality (i.e 2=semi)", "Financial year (360)"}, 
  {1, 0, 0, 1, 0, 0, 0, 0, 0, 0 }, {1, 0, 2015, 1, 0, 2015, 6.75, 4.75, 2, 0} );

  sd:=EVAL(sd); sm:=EVAL(sm);
  md:=EVAL(md); mm:=EVAL(mm);
  sy:=EVAL(sy); my:=EVAL(my);
  days1 := sy+sm/100+sd/10000;
  days2 := my+mm/100+md/10000;
  toReg := sy+mm/100+md/10000; // days to the regulation
  years := my-sy; // years to the maturity
  IF years==0 THEN years:= 1; END;

  IF (finAct==0) THEN
  N:= DDAYS(days1, days2);
  toReg := DDAYS(days1, toReg);
  dayPer := IP(365/ann);
  ELSE
  N:= 30*(mm-sm)+md-sd;
  toReg:= 30*(mm-sm)+md-sd;
  dayPer:= 360/ann;
  END; // if

  price := (coupon/ann)*( (1-1/(1+(yi/(ann*100)))^(ann*years)) / (yi/(ann*100)) ) + 100/(1+(yi/(ann*100)))^(ann*years);
  inter := (coupon/ann)*((dayPer - toReg)/dayPer);
  RECT_P();
  TEXTOUT_P("Days: " + N + " to the end (" + years + " years)", 10, 50);
  TEXTOUT_P("from " + sd + "-" + sm + "-" + sy + " to " + md + "-" + mm + "-" + my , 10, 65 );
  TEXTOUT_P("Price of Bond: " + price, 10, 85);
  TEXTOUT_P("Paid " + ann + " times per year", 10, 105);
  TEXTOUT_P("Interest: " + inter, 10, 125);
  TEXTOUT_P("Press ESC to continue", 10, 150);
  WAIT;
  RETURN {ROUND(price, 3), ROUND(inter,3), ROUND(price+inter,3)};

END;

EXPORT Yield()
BEGIN
  local mesg, days1, days2, toReg, N, finAct;
  local sd, sm, sy, md, mm, my, years, yield;
  local coupon, price, ann, inter, dayPer;
  input ({ {sd,[0],{15,15,1}}, 
  {sm,{"1","2","3", "4", "5", "6", "7", "8", "9", "10", "11", "12"}, {40,15,1}}, 
  {sy,[0],{70,20,1}},
  {md,[0],{15,15,2}}, 
  {mm,{"1","2","3", "4", "5", "6", "7", "8", "9", "10", "11", "12"}, {40,15,2}}, 
  {my,[0],{70,20,2}},
  {coupon,[0],{40,15,4}}, {price,[0], {75,15,4}},
  {ann,[0], {40,15,5}}, {finAct,2,{85,2, 5}}
  }, 
  "Bond YTM: yield to maturity", {"sd", "sm", "sy", "md", "mm", "my", 
  "Coupon", "Price", "annu", "Financial"}, 
  {"Settlement day", "Settlement month", "Settlement year (purchase)", 
  "Maturity day", "Maturity month", "Maturity year (regulation)", 
  "Coupon payment %", "Price now", "n. of annuality (i.e 2=semi)", "Financial year (360)"}, 
  {1, 0, 0, 1, 0, 0, 0, 0, 0, 0 }, {1, 0, 2015, 1, 0, 2015, 6.75, 120, 2, 0} );

  sd:=EVAL(sd); sm:=EVAL(sm);
  md:=EVAL(md); mm:=EVAL(mm);
  sy:=EVAL(sy); my:=EVAL(my);
  days1 := sy+sm/100+sd/10000;
  days2 := my+mm/100+md/10000;
  toReg := sy+mm/100+md/10000; // days to the regulation
  years := my-sy; // years to the maturity
  IF years==0 THEN years:= 1; END;

  IF (finAct==0) THEN
  N:= DDAYS(days1, days2);
  toReg := DDAYS(days1, toReg);
  dayPer := IP(365/ann);
  ELSE
  N:= 30*(mm-sm)+md-sd;
  toReg:= 30*(mm-sm)+md-sd;
  dayPer:= 360/ann;
  END; // if
  C:= coupon; A:= ann; Y:= years; P:= price;
  yield := Solve.SOLVE((C/A)*( (1-1/(1+(X/A))^(A*Y)) / (X/A) ) + 100/(1+(X/A))^(A*Y) = P, X);
  RECT_P();
  TEXTOUT_P("Days: " + N + " to the end (" + years + " years)", 10, 50);
  TEXTOUT_P("from " + sd + "-" + sm + "-" + sy + " to " + md + "-" + mm + "-" + my , 10, 65 );
  TEXTOUT_P("Price of Bond: " + price, 10, 85);
  TEXTOUT_P("Paid " + ann + " times per year", 10, 105);
  TEXTOUT_P("Yield to Maturity: " + ROUND(100*yield,3) + "%", 10, 125);
  TEXTOUT_P("Press ESC to continue", 10, 150);
  WAIT;
  RETURN ROUND(100*yield,3);

END;

[Tim Wessman]

I'd also recommend using FNROOT instead. That is the normal root finder routine that is not an app function.

[salvomic]

(06-01-2015 04:04 PM)Tim Wessman Wrote:  I'd also recommend using FNROOT instead. That is the normal root finder routine that is not an app function.

Thank you Tim, I'll try it soon for my program!

Salvo