Play and Learn 2/19941.ZIP/19941/EDUCMATH/STATS/CORRELAT.BAS

GW-BASIC | 1994-02-04 | 3.1 KB | 59 lines

1  '                   CORRELATION COEFFICIENTS
2  '               Copyright Tracy L. Gustafson, M.D.
3  '              Round Rock, Texas. Version 3.2, 1985
4  ON ERROR GOTO 5000:CHAIN MERGE "EPIMRG",5
15  DIM D(1,1),CS(1,1),N$(1),X(1),X2(1),T(1),MD(1),SD(1)
22  DATA "CORRELATION COEFFICIENTS",27,26
30  LOCATE 6,22:PRINT "1.)  Pearson's correlation coefficient":PRINT
35  PRINT TAB(22);"2.)  Spearman's rank correlation"
40  LOCATE 11,27:PRINT "Enter choice:":AR=11:AC=41:GOSUB 4800:ASUB=VAL(IP$):IF ABS(ASUB-1.5)>0.5 THEN BEEP:GOTO 40
45  AF=0:CLS:ON ASUB GOTO 50,195
50  PRINT TAB(25);"PEARSON'S CORRELATION COEFFICIENT":PRINT TAB(25);STRING$(33,205):PRINT
55  LOCATE 5,1:IF BF=1 THEN 100 ELSE PRINT "     (Enter RETURN if you wish to evaluate significance of a known R value)"
60  LOCATE 4,1:GOSUB 4000:BF=1:GOTO 100
65  AF=1:LOCATE 8,32:PRINT "Enter R value:":AR=8:AC=47:GOSUB 4800:SR=VAL(IP$):SR2=SR*SR
70  IF ABS(SR)>=1 THEN BEEP:LOCATE 25,3:PRINT "Your correlation coefficient should be a decimal fraction between -1 and 1.";:GOTO 65
75  LOCATE 9,25:PRINT "Number of data pairs:":AR=9:AC=47:GOSUB 4800:N=VAL(IP$):PRINT:GOTO 120
80  PRINT:PRINT:PRINT TAB(7);"What are the SAMPLE NUMBERS of the 2 variables you want to correlate?":PRINT:AR=CSRLIN
85  AC=17:GOSUB 4200:NS1=NS:AC=50:GOSUB 4200:NS2=NS
90  IF T(NS1)<>T(NS2) THEN PRINT:PRINT "These 2 samples do not have the same number of elements----":PRINT TAB(32);"a correlation coefficient cannot be calculated.":GOTO 235
95  N=T(NS1):RETURN
100  GOSUB 80:XC=0:FOR Z=1 TO N:XC=XC+VAL(D(NS1,Z))*VAL(D(NS2,Z)):NEXT
105  SC=XC-X(NS1)*X(NS2)/N:SX=X2(NS1)-X(NS1)*X(NS1)/N:
110  SY=X2(NS2)-X(NS2)*X(NS2)/N:SR2=SC*SC/(SX*SY)
115  PRINT:PRINT TAB(20);"Correlation coefficient = ";SC/SQR(SX*SY):PRINT
120  PRINT:V1=N-2:ST=SQR(SR2*V1/(1-SR2))
125  PRINT TAB(7);"Significance of correlation:     T = ";ST;SPC(7);"df = ";V1
130  R=ATN(ST/SQR(V1)):RC=COS(R):R2=RC*RC:RS=SIN(R):X=1
135  IF V1 MOD 2=0 THEN 160
140  IF V1=1 THEN Y=R:GOTO 155
145  Y=RC:FOR Z=3 TO (V1-2) STEP 2:X=X*R2*(Z-1)/Z:Y=Y+X*RC:NEXT
150  Y=R+RS*Y
155  P=1-Y*0.63662:GOTO 170
160  Y=1:FOR Z=2 TO (V1-2) STEP 2:X=X*R2*(Z-1)/Z:Y=Y+X:NEXT
165  P=1-Y*RS
170  PLAY "MS O3 L64 G O2 GE L9 E"
175  PRINT:PRINT TAB(28);"p = ";:IF P<9.99E-07 THEN PRINT "< 10 (-6)" ELSE PRINT P
180  PRINT:COLOR CLR2,CLR1:PRINT TAB(9);"This correlation coefficient is ";
185  IF P>0.05 THEN PRINT "NOT ";
190  PRINT "significantly different than 0";TAB(80):COLOR CLR1,CLR2:GOTO 235
195  PRINT TAB(27);"SPEARMAN'S RANK CORRELATION":PRINT TAB(27);STRING$(27,205)
200  LOCATE 4,1:IF BF=0 THEN GOSUB 4000:BF=1
205  GOSUB 80:CD=0:S2=0
210  FOR Z=1 TO N:FOR T=1 TO N:IF CS(NS1,Z)=CS(NS2,T) THEN CD=Z-T:S2=S2+CD*CD
215  NEXT:NEXT:SR=1-(6*S2/(N*(N*N-1)))
220  PLAY "MS O3 L64 G O2 GE L9 E":PRINT:PRINT TAB(10);:COLOR CLR2,CLR1
225  PRINT TAB(20); "Correlation coefficient = ";SR;TAB(70):COLOR CLR1,CLR2
230  PRINT:PRINT:PRINT " The probability that a given value of Spearman's correlation coefficient is":PRINT "    significantly different than 0 can be evaluated by reference to tables.":PRINT TAB(28);"(See Colton, p. 353)"
235  LOCATE 25,1:PRINT TAB(79):DQ="Would you like to "
240  IF AF=1 THEN LOCATE 25,8:PRINT DQ;:INPUT;"evaluate another correlation coefficient?  ",A$:IF A$="y" OR A$="Y" THEN CLS:GOTO 65 ELSE 255
245  LOCATE 25,2:PRINT DQ;:INPUT;"calculate another correlation using this DATAFILE?  ",A$:IF A$="y" OR A$="Y" THEN 20
250  LOCATE 25,56:INPUT;"a different DATAFILE?  ",A$:IF A$="y" OR A$="Y" THEN BF=0:GOTO 20
255  GOTO 3000
4010  IF FILE$="" THEN 65
4025  ERASE D,CS,N$,X,X2,T,MD,SD
4030  DIM D(A,C),CS(A,C),N$(A),X(A),X2(A),T(A),MD(A),SD(A)
5000  BEEP:IF ERR<>53 AND ERR<>71 THEN 5010 ELSE LOCATE 2,10:PRINT "Please place EPISTAT in drive A: (or other default).":PRINT TAB(25);"Press any key to continue:"
5005  A$=INKEY$:IF A$="" THEN 5005 ELSE RESUME
5010  ON ERROR GOTO 0:END