Schematic presentation of the various steps in the data analysis chain
Although it is possible to define histograms interactively in a PAW session, and then read the (many thousands of) events, in general for large data samples the relevant variables are extracted from the Data Summary Files or DSTs and stored in histograms or an Ntuple. Histograms require to make a certain choice as to the range of values for the plotted parameter, because the binning, or the coarseness, of the distribution has to be specified when the histogram is defined ( booked). Also only one- and two-dimensional histograms are possible, hence the correlations between various parameters can be difficult to study. Hence in many cases it is more appropriate to store the value of the important parameters for each event in an Ntuple. This approach preserves the correlation between the parameters and allows selection criteria to be applied on the (reduced) data sample at a later stage.
In general, the time consuming job of
analysing all events available on tape is run on a mainframe or CPU
server, and
the important event parameters are stored in a Ntuple
to allow further detailed study. For convenience the Ntuple
can be output to disk for each run, and then at a later stage the
Ntuples can be merged in order to allow a global
interactive analysis of the complete data sample (see Figure 
).
A typical batch job in which data are analysed offline and
some characteristics are stored in HBOOK is shown in Figure .
HBOOK is initialised by a call to HLIMIT,
which declares a length of 20000 words for the
length of the /PAWC/ dynamic store. Then the one- and two-
dimensional histograms 110 and 210 are filled respectively
according to the functions HTFUN1 and HTFUN2
and the histograms are output to a newly created file HTEST.DAT.
The output generated by the program is shown in Figure .
PROGRAM HTEST
PARAMETER (NWPAWC=20000)
COMMON/PAWC/H(NWPAWC)
EXTERNAL HTFUN1,HTFUN2
*.------------------------------------------------------------
CALL HLIMIT(NWPAWC)
* Book histograms and declare functions
CALL HBFUN1(100,'Test of HRNDM1',100,0.,1.,HTFUN1)
CALL HBOOK1(110,'Filled according to HTFUN1',100,0.,1.,1000.)
CALL HBFUN2(200,'Test of HRNDM2',100,0.,1.,40,0.,1.,HTFUN2)
CALL HSCALE(200,0.)
CALL HBOOK2(210,'Filled according to HTFUN2',100,0.,1.,40,0.,1.,30.)
* Fill histograms
DO 10 I=1,10000
X=HRNDM1(100)
CALL HFILL(110,X,0.,1.)
CALL HRNDM2(200,X,Y)
CALL HFILL(210,X,Y,1.)
10 CONTINUE
* Save all histograms on file HTEST.DAT
CALL HRPUT(0,'HTEST.DAT','N')
CALL HDELET(100)
CALL HDELET(200)
CALL HPRINT(0)
END
FUNCTION HTFUN2(X,Y)
* Two-dimensional gaussian
HTFUN2=HTFUN1(X)*HTFUN1(Y)
RETURN
END
FUNCTION HTFUN1(X)
* Constants for gaussians
DATA C1,C2/1.,0.5/
DATA XM1,XM2/0.3,0.7/
DATA XS1,XS2/0.07,0.12/
* Calculate the gaussians
A1=-0.5*((X-XM1)/XS1)**2
A2=-0.5*((X-XM2)/XS2)**2
X1=C1
X2=C2
IF(ABS(A1).GT.0.0001)X1=C1*EXP(A1)
IF(ABS(A2).GT.0.0001)X2=C2*EXP(A2)
* Return function value
HTFUN1=X1+X2
RETURN
END
Filled according to HTFUN1
HBOOK ID = 110 DATE 02/09/89 NO = 2
340 -
330 I -
320 I I
310 I I
300 I-I-
290 --I I
280 -I I-
270 I I
260 I I
250 -I I-
240 I I
230 -I I
220 I I-
210 -I I
200 I I -
190 I I-I
180 -I I
170 I I -
160 I I - -I- -
150 I I- I --I I- -I -
140 I I- -I--I I-II-I-
130 --I I- -I I
120 I I - -I I
110 I I I-I I--
100 I I- -I I
90 -I I- -I I----
80 -I I --I I-
70 I I -I I
60 -I I-- - I I- -
50 -I I-- ----I-I I-I-
40 I I-I I---
30 --I I--
20 --I I --
10 -------I I-II--
CHANNELS 100 0 1
10 0 1 2 3 4 5 6 7 8 9 0
1 1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
CONTENTS 100 111222222323222211111 1111111111111111111111
10 1 12224578227034888392975189442985544344445467789101235335456543453430088887545443322111
1. 22345055038484428230601947383077660674994445157562761227948358021717653142735611669210337304276
LOW-EDGE 1. 111111111122222222223333333333444444444455555555556666666666777777777788888888889999999999
*10** 1 0 0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
* ENTRIES = 10000 * ALL CHANNELS = 0.1000E+05 * UNDERFLOW = 0.0000E+00 * OVERFLOW = 0.0000E+00
* BIN WID = 0.1000E-01 * MEAN VALUE = 0.4846E+00 * R . M . S = 0.2199E+00
Fill according to HTFUN2
HBOOK ID = 210 DATE 02/09/89 NO = 4
CHANNELS 100 0 1
10 0 1 2 3 4 5 6 7 8 9 0
1 1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
********************************************************************************************************
OVE * * OVE
.975 * * 40
.95 * ++ 2 2 2++ +3 + ++ + + 2+ 3 2 + 2++++ + 2 + * 39
.925 * + + 2 ++ 32+++ +22 22+ +++ + + + + 22+2+++ +2++ + + + * 38
.9 * 223 +3+ +3 3++333223 +2 2 + + ++2+ + 232+322 2+++ +24+ + * 37
.875 * + ++ +2++++ 342533 443224++2 2 + + ++23 + +42+3222233+++3+++2 22+ ++ + + + * 36
.85 * ++ + 5+35+3333483475 65+2+ + ++ + +33+3 +2 +2335222+235 522 24+ ++ 2 * 35
.825 * ++ 2+2 558335876736583+ 2 +2+ + + 3 224+533623+35252+54 32+452++3 332 +++++ * 34
.8 * ++ + 532 656562546C8A88936324332+ +2+23 +332+2236433657234455556+4635+222 +23 +3 + * 33
.775 * +2 33 375B7274C6A66A782+323++2+23 +5++3+5222256768365258276374+86334+ 32 +++ + * 32
.75 * + 2+ 2 45523786A79FB98B6AD4855224+ + ++23323+5755552468283746644543 443324 5223++ 2 * 31
.725 * + ++4+22+637A785B8BBBA6B4656922++ 2 23 24 2+5464+435552843286C6246623636+3+ 2 3 2 3+2 * 30
.7 * + 22 +2 735ABCA89G8C8A6DA5765+3+322 2+2++52234445475+355864768724+B74632+23 +3 3+ + * 29
.675 * 23 +4+3364HBBAFCFCBB98945C7933++ 2 5+3 +4225243752 75787896C367+475443+32242422 2 + * 28
.65 * + + ++5+3795498GAC96CB9A79E6645 34 3+3 ++24537234424532777657445+4746235+2+3++ 4+2 2 * 27
.625 * + 3 647774A9CE67G99BAB6B233233 4+ 2 322 42 44364+657735+735736733+4+23234 +++++2 + * 26
.6 * + ++3+342233874B8C966896565+5242+5 +2+++++2+5225+42544535456A265357253+2222+ 2+2++ + +2 * 25
.575 * ++ + +5 74535525677984573453422 +2 ++ 2 +++4+2 3526525235+4243342+32+ 23 2+ * 24
.55 * ++ +226+584568349865+433 +2222 + ++ +4444352326542332823+444332 +2 2 + + * 23
.525 * ++++2+65436+3A753535+22+++2+++ ++ + ++2 +2 ++4++2+ 224224+32 2+ ++++ 2 + * 22
.5 * 22 4+23+6425 84543+++42 +2 +++2 2 + 2+2+ 3+ 24++2334223+ 223 +2 + + * 21
.475 * + +5334+7333+22 ++2+ + 3+ 2 +4 +32 2 222+2 + 33++ 222 + +3++ + * 20
.45 * + 433244397 2++23232+ 24 +2 ++ ++2+ 2+ +2+33 ++4 +3 ++2+3 + + * 19
.425 * + ++ 2+ 22+24636432646+5+322 4 +++ + 2++ ++ +22+533+3++3+ +432 +322++2+ 2+ ++ + * 18
.4 * +++3237549588A9725H724545++33+33 + + 2 24 4 +A4633 39 25636343322+82++ ++ + +2+ + * 17
.375 * +++3+374879CCCADLD48996CE54365232 +2+2342347+563264636547B47925542444434+2+322 2+ +2 * 16
.35 * +++ +4637549EC87D8IHDICI9B754655432++23233+2554368886H68B9667889677A635C+4+223333+22 + * 15
.325 * + ++++ 2445949CHHDFNHJRHIHKLDD5DC3545422233 24564875549A8E7899B4F4BC3CA7E597842+67242+++++ * 14
.3 * ++++++2667889EDFEHULQHI*IKFIFA878666336+6+48526B79777BCCEBBAEEED58E96997A4674763463++++ 2+ * 13
.275 * + ++++ 3546898BEMPNIURPH*NOECDC8958E442+3542+68554B37466AAGCEEACAC7A476599962365 343++2 +2 * 12
.25 * + 2344658A9DAJPLDENQGDHJEEBAA93 +3225322+4259A576784DA9B98B56A85CD859797A5843523223+ 22 * 11
.225 * 3 256778BA6CEJGIEAICGCHA4A242+43+++52427545466927A78866BB66795655763454656 2 3 +++ * 10
.2 * +2++4357A69BC88AAFAA5665432+434 +++ ++++343233668554584442CA7664745+4++34+++2 + +++ * 9
.175 * + 3 3436344766755264526++3 2+ + ++ +42 22 2+32345++353562 34 33+++4 +3 +++ + * 8
.15 * 2+ + +3+44+262542+4225 232 ++++ 222 + 2+ +23+242 32+222 2++342 22 22+ 2 + * 7
.125 * + +2 +++22+32+ 3+++2 + +42 + 2+ + + 2+ + + ++ * 6
.1 * + + + +2+ ++ + +2+ + ++ +++ + * 5
.075 * + 2 + + + + * 4
.05 * + * 3
.025 * + * 2
* * 1
UND * * UND
********************************************************************************************************
LOW-EDGE 0 0000000000111111111122222222223333333333444444444455555555556666666666777777777788888888889999999999
0 0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
* I I
* ENTRIES = 10000 PLOT ---------I---------I---------
* SATURATION AT= 31 I 9991 I
* SCALE .,+,2,3,.,., A,B, STATISTICS ---------I---------I---------
* STEP = 1 * MINIMUM=0 I I
Figure: Output generated by job HTEST
Figure: Writing data to HBOOK with the creation of a HBOOK RZ file