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HRP 223 - 2008. Topic 4 – Making and Looking at Data. Toy Data. While it is of little use in real life, SAS lets you manually enter data. First make a library so the data will be permanently stored. Toy Data. Tell it to make the dataset:. - PowerPoint PPT Presentation
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HRP223 2008
Copyright © 1999-2008 Leland Stanford Junior University. All rights reserved.Warning: This presentation is protected by copyright law and international treaties. Unauthorized reproduction of this presentation, or any portion of it, may result in severe civil and criminal penalties and will be prosecuted to maximum extent possible under the law.
HRP 223 - 2008
Topic 4 – Making and Looking at Data
HRP223 2008
Toy Data
While it is of little use in real life, SAS lets you manually enter data.
First make a library so the data will be permanently stored.
HRP223 2008
Toy Data
Tell it to make the dataset:
HRP223 2008
HRP223 2008
If you type a number as the first value of a character variable, EG converts the column to numeric. Right click on the column headings to change them back if this inadvertently happens.
HRP223 2008
Professional programmers equate 0 with “no” and 1 means “yes” but create a format to make reports pretty.
HRP223 2008
Open the data, then set it to be not read only by unchecking the option.
HRP223 2008
When you come back…
If you return to the project it will have forgotten about the formats you applied.
Add a one line program to tell it what libraries (folders) have formats stored in them.
This little program shows the details on formats in a library.
HRP223 2008These 4 records really represent 300 people. So if you were to do a frequency count on the cancer name variable, you would get the wrong count.
Notice that it uses the labels.
HRP223 2008
If you find the label “The FREQ Procedure” annoying, turn it off in the options Tasks > Tasks General pane.
This is the same as the code: ods noproctitle;
You can also set or remove default titles and footnotes here.
HRP223 2008
Fix the title also:
HRP223 2008
Setting the Order
There are options to set the order that the results print. If the options don’t work, make a format.
HRP223 2008
Ordering the Information When data is sorted in format order, the first
“letter” of the alphabet is blank. So put a leading space in the format for the things you want listed first.
I added a leading blank before the Y
HRP223 2008One format is numeric.
The other format is character.
HRP223 2008
Two Categorical Variables
You can do similar voodoo with two categorical variables:
… no idea why Frequency count shows first on the task roles.
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Specify What is a Row vs. a Column
Drag your outcome variable over first. Drag the exposure variable over second.
First
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The character variable lists No before Yes.
HRP223 2008Notice the leading space before the Y.
You could go back and manually change the format by clicking on the column heading in the data set but I recommend just applying it in the analysis.
This will replace values in a character variable so this a character format.
HRP223 2008
Be aware that all the common statistics are here so you do not need to learn the code.
Use the Preview code button to see if you have the right options set.
HRP223 2008
Summarizing Numeric Data
Begin with a graphic.– Remember that you want to show both central
tendency and variability.– You have already briefly seen the Summary
Statistics and Distribution Analysis menu options (aka proc means and proc univariate).
I want you to know how to summarize large and small datasets.
HRP223 2008
Numeric Data Say somebody tells you to simulate rolling dice. The formula to do this says:
– generate a random number between 0 and 1– multiply it by 6 – round up to the closest integer
data die;*the 22 says which list of numbers between 0 & 1;aNumber = ranuni(22);die = ceil(6*aNumber);* Generate a random integer between 1 and 6.;dieDie = ceil(6*ranuni(78687632));output; * write to the new dataset;return; * go to the top and try to read in data;
run;
HRP223 2008
Doing Stuff Repeatedly How to roll two dice:data dice;do x = 1 to 2 by 1;roll= ceil(6*ranuni(78687632));output;end;return; * go to the top and try to read in data;
run;
HRP223 2008
Craps… In the dice game “craps” you throw two dice and the number you roll
determines if you win or lose. How do you simulate rolling 10 pairs of dice?
data craps ;do trial = 1 to 10;do dieNumber = 1 to 2;roll = ceil(6*ranuni(78687632));output;end;end;return;
run;
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The Total
Calculate the sum across the rolls using Summary Statistics on the Describe menu.
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Total on a Trial
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Do the histogram on the summary data.
HRP223 2008
Crank up the number of simulations. Turn off the histograms for each trial.Generate a histogram based on the 1000 trials.
I want to fix the way the histogram is binned.
When the code is open, push any key and it will make a copy of the code which you can edit.
HRP223 2008
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Do Loops
Loops are used whenever you need to repeatedly do something. Say you wanted to read in 24 lines of data, where the first 6 records are from 1 treatment, the next 6 are from a 2nd, etc.
HRP223 2008
More Condensed
The group could be a counter that goes from 1 to 4.
HRP223 2008
How to Summarize
You can get a boxplot or a histogram with only 6 values but they will not be very informative.
HRP223 2008
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Only a Few
If you only have a few data points, you should consider a mean and dot plot. SAS doesn’t have one built in so I made a macro to do it.
Macros are self contained blocks of code that do complex things. – A good Macro is like a function. You pass it a few
arguments and it returns an answer. You don’t need to look at how its guts work.
HRP223 2008
The plotit Macro
You paste in the macro beginning with the macro line and ending in the mend line.
Then you invoke the macro using the name following the %macro statement:
HRP223 2008
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Macro Stuff
Macros can do simple formulas like calculating an age.
Or really ugly stuff like validating dates.
HRP223 2008
HRP223 2008
Function Help
The books for the class have lists of frequently used functions but you probably want to bookmark the function help in EG as well as using onlineDoc.
HRP223 2008
Add it to the favorite page.
Highlight a word in the right windowpane and then type control-f to find words.
HRP223 2008
Dummy records in the HW
Recall there was a dummy record at the beginning of the Homework datasets. Why?– Columns of data in Excel are allowed to take
arbitrary widths. So if you have a “last-name” column it will import into a database as having the width of the longest name.
– If you import a second dataset and it has a different length and you try to append them together a database will choke.
– You can use a dummy record to make sure the columns have the same length.
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Combine two datasets
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HRP223 2008