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Technical posts that have to do with CANDAT software, should not appear in Course other than through links.

Food Profile Utility

This utility  has been extracted from the more general CANDAT and shares features with it. Familiarity with this utility will prepare your entry into the other features of CANDAT. CANDAT is consistent and intuitive in its usage.

You need a bit of familiarity with some keystrokes:

  1. Esc Chooses the last choice of a menu or exits the active task
  2. F6 The information key. Give you a choice of valid codes or allows you to enter keywords which will generate a list of entries. Choosing one of those entries (and pressing Enter) will insert the proper code

The “pro” version of this utility allows you to print the profile or export its data to a spreadsheet readable format.

SPSS or SAS or PSPP or … and CANDAT

SPSS, SAS  (or other good statistical packages) is used to process Candat calculations into results for your scientific report.

At its most detailed Candat will produce data files consisting of:

  • Subject code
  • Date
  • Day of Week code (0-6, where 0 is Sunday)
  • Food Group code
  • Meal code
  • Food code
  • Food description
  • Nutrient variables (Weight of foods and all nutrients you selected at reporting)

The printed (text or PDF) file (hopefully you did not print to paper) can have all of the above information as well as basic statistics (for a quick perusal, not meant to be used instead of a statistical package).

Candat also produces computer readable files that can be directly read into statistical packages or spreadsheet software (such as Excel or Open or Libre Office Calc or ….) . . Your study will probably want to make use of daily average intake data, as representative as possible of your subject’s usual intake.

Where you have days of the week and weekend days you will probably want to make use week-weighted average daily intakes, where weekend days carry less weight than week days. These week-weighted averages are calculated in Candat but should be re-calculated in the statistical package so that you can make use of the proper variance calculations for weighted data.

Systematically then here are the procedures to follow for managing your data:

  • Generate the data in Candat you need in a compact way. If you are not interested in data by meals or by food group or at the food detail level, leave those out of the Candat calculation.
  • Read the Candat generated file into a statistical package
  • Identify missing data as -1 (the Candat value at the food level. In Candat summaries (means) missing values are considered a zero. This makes sense because food databases do not spend much time analyzing nutrients that are not likely to exist in the food but they do not report them as having a value of zero (usually).
  • Convert the Day of Week code to a weight to be used in week weighted calculations. In Candat we use 5 for codes 1 to 5 and 2 for codes 0 and 6.
  • Weight the cases using the converted Day of Week variable
  • Aggregate the cases. In most cases you will want to aggregate the data using Subject code and Date code as independent variables, an average weight code for the weighting variable (average will maintain the weight code for the day)  and sum (which adds up all the contributions for that day) for the nutrient variables. At this point your data is ready for statistical processing.
  • Apply exploratory statistics to all your variables and make sure the data seems reasonable
  • Merge the data variables that identify your subject variables. This may be from a file produced externally from Candat or from the Candat Description file.  In either case you must make sure to merge on the Subject codes.
  • Compare your subjects to your control groups (subject variables) using statistical procedures and save the results.

Report these results, write the other sections of the paper and you are done.

 

Week-weighted Averages in CANDAT

When expressing and comparing results of multi-day (3 day commonly) food recalls one tends to use the average daily intake as a measure of a subject’s intake. Of course, 7 day recalls will give more accurate estimates of this daily intake and the accuracy will increase if all the days of a week are used. The assumption here is that subjects will eat differently on different days with the greatest variability been between week days and weekend days.

Rather than simply computing an average daily intake one may get more accurate results by weighting the days of the week and the weekend days differently.

A weight of 5 for each week day and a weight of 2 for weekend days should allow us to calculate week-weighted averages for any number of recalls. Of course, for recalls without weekends this would just be a day of the week average and vice-versa.

The week-weighted average could be calculated as follows:

xw = (∑ wi × xi) ÷ ∑ w

where xw is the weighted average with  xi as the daily intakes, and i is 1 – 5 (codes for days of the week) or 0,6 codes for weekend days corresponding to Sunday and Saturday respectively. w1-5 would then be 5 and w0,6 would be 2.

with a variance of

Var(xw) = Var(x) × ((∑ wi2) ÷ (wi)2)

where Var(x) would be the variance over all the days of the food intakes for the subject.

How can I identify when and where my subjects ate their food?

The researcher can enter meal codes from 1 to 999. A typical way of using these codes is to set 1 to 9 as the first digit, 0 to 9 as the second digit and 0 to 9 as the third digit. For instance this could make 100 breakfast, 110 breakfast away, 111 breakfast at MacDonalds, etc… of course, any scheme is possible using these 3 digits.
The researcher can enter this data in a table of meal codes which are used to prompt data entry personnel and provide output in validation reports. This table is subject file specific. A meals table can thus be specific to each study.
Meal codes and descriptions appear in all meal detail reports. Meal codes are included in export files and can thus be used in spreadsheets and statistical packages.

View food and meal descriptions by pressing “F1” over the code

When reviewing data input it is now possible to see the descriptions of the food and the meal codes that have been entered. Pressing the “F1” key at the top left of the keyboard will show the description for about 2 seconds. If that is too long for you simply press another key. A quick way to go through all your input for foods is to simply go to the first food code, press F1, glance at the result and then press the arrow down key to go to the next food. You will need to press the arrow down key twice (if you are fast), once to remove the description of the active food and once to go to the next food. Pressing “F1” again shows you that food’s description. It can become a quick two finger action, very efficient.

The time the description is shown can vary. You can set a longer time using the system message utility. Again, pressing any key will remove the description and allow you to proceed.

The F1 key has also been implemented for the quantity field. Pressing F1 while in that field will show the food quantity in grams and its energy value based on the quantity and unit codes entered.

How do I know that all the foods in my study fall into my defined food groups?

In Task 300 you can create a table of unique food codes that appear in your subject file. Candat will go through all of your selected subjects and store the unique codes found in a table of your choosing. Once done you can go to task 210, the food groups definition task and choose the food category of interest. By pressing slash (“/”) you will get a secondary menu which allows you to work with the categories. One of the options here is the “Validate group definitions” option. This will create a listing for you which will show, for all the foods in your unique foods table, the group in which they will fall. If there is no code beside a food it means it will fall outside the defined groups and appear as such in your nutrient reports by group feature (Task 340).

Folate and Vitamin A and other nutrients in CNF 2010

The most recent version of the Canadian Food File (CNF) deals with Folate and Vitamin A differently. Please read the User guide (a free download with the trial version of CANDAT10) to get an understanding of the logic behind the changes. Once you have done this simply run a Food Profile within CANDAT and look at the available nutrients and their codes. This will give you an insight into the changes in this new version of the CNF. You can also run a nutrient distribution report (Task100, Option 3) to see all the available nutrients and their relative presence in the foods.

Folate and Vitamin A and other nutrients in CNF 2010

The most recent version of the Canadian Food File (CNF) deals with Folate and Vitamin A differently. Please read the User guide (a free download with the trial version of CANDAT10) to get an understanding of the logic behind the changes. Once you have done this simply run a Food Profile within CANDAT and look at the available nutrients and their codes. This will give you an insight into the changes in this new version of the CNF. You can also run a nutrient distribution report (Task100, Option 3) to see all the available nutrients and their relative presence in the foods. In particular this is important for folate. Folate used to have nutrient code 435, it is now 815.

Food Files

CANDAT uses as its Master file the Canadian Food file. This Master file is included with CANDAT. CANDAT can also accommodate a second or alternate Master food file (such as the USDA Handbook #8 file).

  1. Food code: The code structure used is identical to that used by the Canadian food file. An extra zero has been added to the end of the 6 digit code to allow the institute and user files to fold new food codes into the same code areas as that of the Master food file.
  2. Tier Structure: CANDAT has a three tiered food file structure. The first tier contains the Master food file. CANDAT does not allow direct changes to be made to this file. The next tier contains the Institute file. There is only one such file and CANDAT is installed with this file empty. The third tier contains the User food files. There can be any number of User food files though only one can be active at a time.
    The concept of the three tier system also allows an institution to define values for foods to be used in analysis by all its users. Values the institution may consider less accurate than desired in the Master food file can be entered and used from the Institute food file. The food information is copied completely from the Master file and stored in the Institute file where it can be changed, under password control, by the manager of the system.
    The same concept applies to the User food file in relation to both the Master food file and the Institute food file. When CANDAT needs food information it first looks to the User food file, then to the Institute file and finally, to the Master food file. Identical food codes are used at each tier so that finding the food has the effect of masking the level(s) above it.

Output to save files

Reports that are the result of nutrient calculations can be output to files that you can either open with a word processor or import into a spreadsheet environment (like Excel) or adatabase environment (like SAS, SPSS or other statistical package) . You are prompted for a file name and different files are created using those names in your user save area. Use eight characters only for file names, no spaces and no special characters. CANDAT will append various extensions to these files so that they are readily identifiable. All such files will be created in the user folder, sub-folder save,  identified at CANDAT installation.

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