Sunday, November 26, 2017

Rounding to the Nearest Reciprocal (HP Prime, TI-84 Plus CE, Casio fx-CG 50)

Rounding to the Nearest Reciprocal   (HP Prime, TI-84 Plus CE, Casio fx-CG 50)

Introduction

The program ROUNDRCP rounds a number to the nearest 1/n. This function can come in handy in several applications, for example, when working with construction or measuring, when have to round results to the nearest eighth (1/8), inch (1/12) or sixteenth (1/16).

Presented here are versions for the HP Prime, TI-84 Plus CE, and Casio fx-CG 50.

HP Prime:  ROUNDRCP

EXPORT ROUNDRCP(a,n)
BEGIN
// Round a to the nearest 1/n
// 2017-11-21 EWS
LOCAL w;
w:=FP(ABS(a))*n;
w:=ROUND(w,0);
RETURN IP(a)+SIGN(a)*(w/n);
END;


The TI-84 Plus CE and Casio fx-CG 50 versions store the answer in X.

TI-84 Plus CE ROUNDRCP

"EWS 2017-11-21"
Input "NUMBER:",A
Input "TO 1/NTH:",N
fPart(abs(A))*N→W
round(W,0)→W
If A<0
Then
iPart(A)-(W/N)→X
Else
iPart(A)+(W/N)→X
End
Disp "X:",X


Casio fx-CG 50 ROUNDRCP

“NUMBER”?→A
“TO 1÷NTH”?→N
Frac ((Abs A))*N→N
RndFix(W,0)→W
If A<0
Then
Int (A)-(W÷N)→X
Else
Int(A)+(W÷N)→X
IfEnd
“X:”
X

Examples

Round π to the nearest 1/4:
ROUNDRCP(π, 4):  3.25 = 13/4

Round e^2 to the nearest 1/100:
ROUNDRCP(e^2, 100): 7.39 = 739/100

Round 1/4 + 2/7 + 3 1/3 to the nearest 1/16:
ROUNDRCP(1/4 + 2/7 + 3 + 1/3, 16):  3.875 = 31/8
(thank you to Joe Horn for pointing out my error, it's correct now.)

Tips 

If you do not have the sign (signum) function, you can compensate by the following code:

If X<0
Then
Return -1  (subtract operation)
Else
Return 1 (addition operation)
End

If your calculator does not have the Round to any number of decimal points function, such as the Casio fx-5800p or fx-3650p, you can manipulate the modes and use the Rnd function and a switch of modes, like this code:

Fix 0
X  (put number to round in display)
Rnd
Float/Norm (1/2)

Eddie


This blog is property of Edward Shore, 2017

1 comment:

  1. The pivot-calculator is used to calculate pivot points in order to make the right decision while trading. A pivot point is the price at which the price fluctuation of a currency pair is expected to move into a different direction.

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