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Frequently Asked Questions (FAQs) / Notes
Throughout the HEDS web site, EPA provides users with information to help them understand the data available from HEDS and to use it effectively. The How to Use HEDS--First Time User's and How to Use HEDS--Reference documents, available by clicking on the links in the navigation bar, provide useful information about how to use HEDS and about how the data and metadata available from HEDS are organized. These Frequently Asked Questions (FAQs) and Notes provide capsulized pointers for some of the more common questions about using HEDS. In addition, these FAQs and Notes provide general information about each HEDS study. They also provide details about any data and metadata that may not be included in the current download packages.
FAQs
Notes--HEDS Studies
How do I find out what data are available in HEDS?
On any HEDS page, click the HEDS Studies link. The HEDS Studies page shows available projects and studies.
What is the difference between a project and a study?
A project consists of one or more studies.
What is an Entry ID?
An Entry ID is the number associated with a study, data set, or document in the EIMS database.
How do I find out the Entry ID for a data set or document?
On the HEDS Study Information Directory page, click List of Data Sets or List of Documents.
Why do I need to go back and forth between EIMS and HEDS?
EIMS is an EPA database that contains metadata for many EPA projects, including HEDS. EIMS contains metadata for HEDS data sets and HEDS documents. This metadata provides information regarding an entry to help you determine whether or not the entry meets your needs. HEDS has the functionality for accessing the actual data sets.
When I am viewing an EIMS Metadata Report for a document, how do I access the document?
On the EIMS navigation bar, under Report Sections, click Downloads. Then click the Complete Document link.
When I am viewing an EIMS Metadata Report for a data set, how do I access the data set?
On the EIMS navigation bar, under Report Sections, click Downloads. Then click the Download Data Set link.
How do I find out what data columns are in a data set?
On the Download Complete Data Set page for the data set in question, click Browse Data Dictionary to view the data dictionary online, or click Download Data Dictionary to view the data dictionary offline.
Can I preview a data set before I download it?
Yes. On the Download Complete Data Set page, or on any page with the menu box at the top, click Browse Data Set to view the first 10 rows.
What if I want only part of a data set?
You can select the columns you want. Row selection is not available. See Select Data Set Columns in How to Use HEDS--Reference.
I have clicked on a link in the Customized Data Set section of the menu and then clicked on a link in the Complete Data Set section. Why have the links in the Customized Data Set section become inactive?
The Customized Data Set section is active only when clicked. The section is inactive and any selection you have made is canceled if you then click a link in the Complete Data Set section.
When I am selecting columns from a data set, why won't HEDS let me deselect the highlighted columns?
The highlighted columns are record identifying columns and will be part of any customized selection.
What if I change my mind about the columns I selected?
If you are still on the Select Data Set Columns page, you can uncheck the selected columns you want to exclude. You can also click Clear to deselect all the selected columns and then make a new selection.
If you have moved on to the Selected Data Set Columns page, you can click your browser's Back button to return to Select Data Set Columns page, make changes as described above, and re-Submit your selection. Alternatively, you can click Select Columns in the menu box at the top of the page and start over.
I use the Internet Explorer browser. When I download a customized data set (or data dictionary or code set), the information appears in the browser window. How do I get this information to a file?
See Important Download Information for Internet Explorer Users in How to Use HEDS--Reference.
I downloaded a complete data dictionary for one data set. When I downloaded a second data dictionary, I lost the first file. What do I do?
Files are saved with the same filename every time. It is recommended that you assign a unique filename to each file to be downloaded.
What do the data dictionary and code set information on columns and variables have to do with the data set?
The data dictionary provides characteristics of the data columns in a given data file. This information is useful when reviewing or analyzing the data. The code set provides the map between the code values used for the responses in the data and the descriptions those code values represent.
When I try to import the data into my software, why do none of the labels appear?
Different software applications handle HEDS files differently. See Importing dBase IV (.dbf) Files and Importing ASCII (.txt) Files in How to Use HEDS--Reference.
Why are there multiple data set (ds), data dictionary (dd), and code set (cs) files in a complete download package?
Data sets have a maximum of 255 columns, to allow import into a wide range of software. If a data set has more than 255 columns, it is split into segments. The data dictionary and code set are split to match the data set segments.
Note, however, that because complete data dictionaries and code sets never have more than 255 columns, it is not necessary to split them. The complete download package will therefore also include complete data dictionaries and code sets.
I downloaded a complete data set, and I also downloaded a complete data set using the customized option. Why aren't my files the same from both downloads?
The files will have the same data. However, under the customized option the columns may be grouped differently.
I downloaded a complete data set in ASCII format, and when I imported it into SPSS, I lost the column names. How do I get the column names to be included?
In ASCII downloads, column names are surrounded by double quotation marks (").
SPSS does not accept quotation marks. See
Why does the COL_NUM for a given data column in the complete data dictionary not match the COL_NUM for the same variable in the segmented data dictionary?
Data columns are grouped differently in segmented files.
How do I determine the code descriptions for a particular data column?
In the code set files, find the rows that have the same COL_NAME as the data column of interest.
What are missing values?
Missing values are values usually associated with nonresponses or data that are not available. Some analytical software tools allow a user to define missing values for a data column. This software option enables a user to include or not include in an analysis any rows that contain the assigned missing values.
What is a primary key?
A primary key is a data column or columns that provide for a unique identification of each row in a data set.
In an analytical results file, what is an1c column?
Some HEDS studies include ancillary data columns for an analytical result. These columns are designated as an1c, an2c, and so on.
Why is there only a complete data dictionary for a customized selection?
Downloading a data dictionary separately from the package gives only a complete data dictionary file with no segments, even if segments are included in the data set package.
Why are the units in the data dictionary for analytical results blank?
If all units for a data column of analytical results (e.g., UNTCM001) are the same, the units will be given in the data dictionary. If there is more than one type of unit associated with the data, the units column in the data dictionary is left blank. The units for each result are in the associated units column.