COMBINE FREQUENCY TABLE

COMBINE FREQUENCY TABLE (LET)

Let Subcommand

Combine low frequency bins in a frequency table.

For grouped data, Dataplot typically expects equal width bins. However, there are occasions where you want to combine bins with low frequencies. For example, for the chi-square goodness of fit test it is recommended that the minimum frequency be at least five in order for the chi-square approximation to be valid. This command allows you to automatically combine bins that are below a specified count (5 by default).

LET <y2> <xlow> <xhigh> = COMBINE FREQUENCY TABLE <y1> <xmid>
                        <SUBSET/EXCEPT/FOR qualification>
where <y1> is a variable containing the original frequencies;
            <xmid> is a variable containing the bin mid-points;
            <y2> is a variable where the combined frequencies are stored;
            <xlow> is a variable where the lower limits for the combined bins are stored;
            <xhigh> is a variable where the upper limits for the combined bins are stored;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

LET Y2 XLOW XHIGH = COMBINE FREQUENCY TABLE Y XMID

You can specify the minimum frequency for a bin by entering the command
LET MINSIZE = <value>

before the COMBINE FREQUENCY TABLE command.

The following commands currently accept grouped data with either equal size bins or unequal size bins:
PROBABILITY PLOT
PPCC PLOT
KS PLOT
CHI-SQUARE GOODNESS OF FIT

The minimum frequency for a bin defaults to 5.

None

BINNED	= Convert raw data to grouped data.
CHI-SQUARE GOODNESS OF FIT	= Perform a chi-square goodness of fit test.
PROBABILITY PLOT	= Generate a probability plot.
PPCC PLOT	= Generate a ppcc plot.
KS PLOT	= Generate a Kolmogorov-Smirnov (or chi-square) goodness of fit plot.

Distributional Modeling

2004/10

 
LET Y = LOGNORMAL RANDOM NUMBERS FOR I = 1 1 100
LET Y1 XMID = BINNED Y
PRINT Y1 XMID
LET Y2 XLOW XHIGH = COMBINE FREQUENCY TABLE Y1 XMID
PRINT Y2 XLOW XHIGH
TITLE AUTOMATIC
Y1LABEL CORRELATION
X1LABEL SIGMA
LOGNORMAL PPCC PLOT Y2 XLOW XHIGH
    

 VARIABLES--Y1             XMID    

   0.6000000E+01  0.2812552E-01
   0.2000000E+02  0.4171193E+00
   0.2400000E+02  0.8061130E+00
   0.1400000E+02  0.1195107E+01
   0.1300000E+02  0.1584100E+01
   0.7000000E+01  0.1973094E+01
   0.5000000E+01  0.2362088E+01
   0.1000000E+01  0.2751082E+01
   0.1000000E+01  0.3140075E+01
   0.1000000E+01  0.3529069E+01
   0.1000000E+01  0.3918063E+01
   0.3000000E+01  0.4307056E+01
   0.0000000E+00  0.4696051E+01
   0.2000000E+01  0.5085044E+01
   0.1000000E+01  0.5474038E+01
   0.0000000E+00  0.5863031E+01
   0.0000000E+00  0.6252026E+01
   0.0000000E+00  0.6641019E+01
   0.0000000E+00  0.7030013E+01
   0.1000000E+01  0.7419006E+01


 VARIABLES--Y2             XLOW           XHIGH   

   0.6000000E+01 -0.1663711E+00  0.2226222E+00
   0.2000000E+02  0.2226226E+00  0.6116159E+00
   0.2400000E+02  0.6116164E+00  0.1000610E+01
   0.1400000E+02  0.1000610E+01  0.1389603E+01
   0.1300000E+02  0.1389604E+01  0.1778597E+01
   0.7000000E+01  0.1778598E+01  0.2167591E+01
   0.5000000E+01  0.2167591E+01  0.2556585E+01
   0.1100000E+02  0.2556585E+01  0.7613503E+01