| Groups available: | ||
| Top Read & Start - Folders and Files | |
| Control set parameters | Set < parameter > Set parameters control how much information you get in the output window (e.g. set statistics), how commands are executed (e.g. set replacedatafile) and other aspects Set just issue "set" with no words after to see which ones are defined. |
| Folder changes | cd "name/folder"
To make a particular folder the working folder either use a "cd ......." command in the epidatastat.ini file or define this in the lnk where you start epidata analysis. |
| Top Basic analysis | |
| Select by date - existing variable | Select <logical criteria>
Solution: use the built in formulae. Adapt according to your date format (dmy/mdy/ymd) |
| Select by date - create date variable | Assume you have age in 1996 in field: age new var date born; new var int yearborn := 1996 - age; born = createdate(1, 7, yearborn); select born < createdate(12, 2, 1988); //select all born before 12th of february 1988 begin ... end |
| Test if a string variable contains legal dates | You have read a text (delimited) file, and wish to convert a string variable to a date Assumed variable names: The string variable with dates is "txtdate", ID is id number. read myfile.csv var // to see the variables * Now convert to date: gen d mydate = date(txtdate) // Incorrect date values will be "." gen d mydate1 = date(txtdate,"V") // Incorrect date values will be "01/01/1980" gen i mydateok = (mydate = mydateok) // 0 if they are the same, 1 if different tables mydateok // to see the count select if mydateok = 1 list id txtdate mydate mydate1// to see the values select list id txtdate mydate mydate1 if mydateok = 1 // alternative to select |
| Check for missing data in several variables |
Generate an indicator variable: m
define m _____________________________ if v1 = . then m = trim(m) + "N" else mv = mv + "V" if v2 = . then m = trim(m) + "N" else mv = mv + "V" etc. for all other variables, freq m * alternative solution: m = "" m = trim(m)+string(mv(sex)) // function mv = 0 for actual value m = trim(m)+string(mv(age)) // function mv = 1 if variable=. m = trim(m)+string(mv(km)) // function mv = 2 if variable=defined missing value tab m |
| Top Basic graphs | |
| Split Y variable | Assume you wish to make a scatter plot of Haemoglobin Values by age where males are circles and females filled circles. Scatter age Hb by sex would be convenient, but You cannot do that since "by sex" is not allowed. Solution: Assume sex is 1 for males and 2 for females, Hb is Haemoglobin gen male = Hb if sex = 1 gen female = Hb if sex = 2 Scatter age male female /ti="My nice graph of variable Y by sex" /sub="With this subtitle" |
| Add text for Y-axis | Solutions. E.g. for scatter plot to add "y=log(age)"
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| Top Output | |
| Change Output Colour and design | Desing of output is controlled by a "stylesheet" contained in epiout.css which you can edit. Several web sites and books explain more on how to use stylesheets. To change background for tables to white: 1. Open the epiout.css file in the editor found where EpiData Analysis is installed 2. Change this line: table {background-color:black; border: solid #000 3px; width: 500px; } to table {background-color:white; border: solid #000 3px; width: 800px; } and for the cellcontents change color to black or other color or contents are invisible. E.g.: .firstcol {color: black;font-size: 10pt;font-family: verdana; font-weight: normal; text-align: right; padding-right:10px; } 3. Save the css file as Whitetable.css and use by set stylesheet="whitetable.css" Submit examples to info@epidata.dk for dissemination to other users. See further explanation in document: Formatting output |
| Top Generate/change variables | |
| Boolean Variables | define lonely <Y>
This would define a Boolean variable. To add values use: lonely = True lonely = False |
| Top Clean up & stop | |
| Top Dates and date variables | |
| What are dates | In EpiData Analysis dates are used internally as the number of days since 1899/12/30 but shown in a known date format, such as
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| Exclude date from table | Assume you have assigned Jan. 1st 1800 as the missing value in a date variable "born" select born <> createdate(1,1,1800) freq born |
| Calculate age on day of visit | Assume you have date of birth in variable DOB and date of visit in VISIT new var int agedays := visit - dob // days new var int ageyear := integer(agedays / 365.25) // years |
| Calculate age on day of visit - simulation example | To see the example you can use this code: close generate 10 gen d dob = dmy(15,1,(1930+5*_n)) gen d visit = dmy(15,_n,2007) gen i age = trunc((visit-dob)/365.25) gen i age1 = round((visit-dob)/365.25) gen age2 = (visit-dob)/365.25 list
Notice that by rounding you get incorrect age, whereas truncating gives the correct one. |
| Select by date - create date variable | Assume you have age in 1996 in field: age
define born <dd/mm/yyyy> gen yearborn = 1996-age born = dmy(1,7,yearborn) Select born < dmy(12,2,1988) //select all born before 12th of february 1988 |
| Test if a string variable contains legal dates | You have read a text (delimited) file, and wish to convert a string variable to a date Assumed variable names: The string variable with dates is "txtdate", ID is id number. read myfile.csv var // to see the variables * Now convert to date: gen d mydate = date(txtdate) // Incorrect date values will be "." gen d mydate1 = date(txtdate,"V") // Incorrect date values will be "01/01/1980" gen i mydateok = (mydate = mydateok) // 0 if they are the same, 1 if different tables mydateok // to see the count select if mydateok = 1 list id txtdate mydate mydate1// to see the values select list id txtdate mydate mydate1 if mydateok = 1 // alternative to select |
| Top Information | |
| Top Further analysis | |
| Regression | Logistic Outcome Indicator Confounder ...... You cannot do Logistic Regression or other advanced statistics. Use other software. Data can be exported with labels to Stata (www.stata.com), SAS, SPSS and as delimited files to other software. |
| Top Special graphs | |
| Top Special data handling | |
| Top Disk commands | |