Trailing-Edge
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PDP-10 Archives
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decus_20tap1_198111
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decus/20-0025/dplotx.txt
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00100 THIS PROGRAM INTEGRATES UP TO FOUR FIRST-ORDER DIFFERENTIAL
00110 EQUATIONS BY THE FOURTH-ORDER RUNGE-KUTTA METHOD AND GIVES THE
00120 CHOICES OF SEEING A PRINTOUT OF THE INTEGRATED VALUE(S) AND
00130 THE PLOTTED FUNCTION(S).
00140
00150 THE START POINT, END POINT, AND THE SETPSIZE ARE ENTERED AS DATA
00160 ON LINE 100.
00170
00180 THE DIFFERENTIAL EQUATIONS ARE ENTERED ON LINE(S) 110 THRU 140
00190 INCLUSIVELY.
00200
00210 IN ORDER TO USE THE PROGRAM IT IS NECESSARY TO INCORPORATE THESE
00220 OR SIMILAR SUBSTITUTIONS:
00230
00240 LET: DX/DT=D(1) AND X=Y(1)
00250 DY/DT=D(2) AND Y=Y(2)
00260 DZ/DT=D(3) AND Z=Y(3)
00270
00280 AND SO ON FOR AS MANY AS FOUR VARIABLES.
00290 FOR EXAMPLE:
00300
00310 INTEGRATE THE FOLLOWING SYSTEM OF EQUATIONS
00320 DX/DT=Y
00330 DY/DT=-4X
00340 DZ/DT=2Z
00350
00360 FROM T=0. TO T=2., WHERE THE INITIAL VALUES FOR X, Y, AND Z ARE
00370 0, 2, AND 1 RESPECTIVELY.
00380
00390 THE INPUT IS AS FOLLOWS:
00400
00410 *100 DATA 0,2,.0625
00420 *110 LET D(1)=Y(2)
00430 *120 LET D(2)=-4*Y(1)
00440 *130 LET D(3)=2*Y(3)
00450 *RUN
00460
00470 WHEN THE PROGRAM IS IN THE PROCESS OF RUNNING IT WILL ASK FOR
00480 THE INITIAL GUESSES FOR THE AMOUNT OF VARIABLES GIVEN IN THE
00490 EQUATIONS. IT GIVES THE OPTIONS OF VIEWING A PRINTOUT, A PLOT,
00500 OR BOTH.
00510
00520 THE CURRENT STEPSIZE IS PRINTED BEFORE THE PRINTOUT AND THE
00530 PLOT. THE PROGRAM GIVES THE CHOICE OF CHANGING THE STEPSIZE.
00540
00550 AFTER THE OUTPUT HAS BEEN DISPLAYED THE PROGRAM CALCULATES A NEW
00560 START POINT, A NEW END POINT, AND SAVES THE LAST CALCULATED
00570 VALUES OF THE INTEGRATED FUNCTION(S) AS THE NEW INITIAL GUESSES.
00580 IT THEN GIVES THE CHOICE OF SEEING MORE OUTPUT STARTING AT THIS
00590 POINT.
00600
00610 END OF INSTRUCTIONS.