Preparing a data table: Not all that complicated !!!

Photo : André Gagné

Photo : web

Photo : web

By : The CEF professionals

2007

Why this presentation?

• To avoid the enormous waste of time often associated with repeated but avoidable data handling.

• To facilitate ready understanding of the data set, even many years after it was first created!!!

?

Data sheets (1/2)

• Write legibly.

• Anticipate who might make use of the data.

• Include the date.

• Organise by line…

• Anticipate any contentious cases & try to work around these (% closing of forest cover ou opening ?!)

Data sheets (2/2)Fiche placette centrale 400m²

Date: Equipiers

Coordonnées

Peuplement Azimut

Altitude

% fermeture au centre: Exposition

Pente

Inventaire écoforestier:Densité: Pente: Situation topo: Texture sol:Hauteur: Exposition: Type d'humus: Type dépôt :Perturbation: Drainage: Prof. Humus: Prof. Dépôt:

Arbres sur pied (vivants ou morts)(dhp>9 cm)

No EspèceDHP (2

cm)État (9

classes)No Espèce

DHP (2 cm)

État (9 classes)

No EspèceDHP (2

cm)

État (9 classes

)

Localisation : chiffre site

Remarque :

The Data Table

Names of variables (1/5)

• Keep as simple & short as possible, but still comprehensible!

• One variable = one column• Several times for the same variable = several columns

• Break up complex categories: e.g., irrigated & fertilised balsam fir in block 2

To break up the indicators: fir tree irrigated and fertilized in block 2

bloc espece fertilisation irrigation traitement

2 sab oui oui 2-sab-fer-irr

sujet temps1 temps2 temps3

a 10.2 14.3 18.7

The Data Table Names of variables (2/5)

• Place class or categorical variables at the beginning of the table, followed by the response variables.

• Whether using capital or small letters, be consistent, as certain programs are case-sensitive (R)!!!

• Things to avoid :– Special characters (/$%?&)– Spaces

Be clear and precise, and include a comment sheet where all abbreviations are explained

OR

If you are in Excel, use «Insertion / Comments»

Names of variables (3/5)

latéralelatérale

Names of variables (4/5)

• The «remarks» column in a data sheet = imparts flexibility to a data table by allowing:

–inclusion in an analysis

or

–exclusion from an analysis

CHECK YOUR DATA

Names of variables (5/5)

• Avoid the pain of having to start the process all over, or having to make more or less complex data manipulations.

Date Point Parcelle Echelle haut midh midb bas502 1 A 10 50 40 20 70502 1 B 10 0 0 10 10502 1 C 10 0 0 10 10502 1 D 10 40 50 40 50502 1 I 25 0 70 100 100502 1 J 25 0 0 25 70502 1 K 25 95 90 90 60502 1 L 50 50 60 70 50502 1 M 50 60 50 80 70502 1 N 50 95 85 95 100515 2 A 10 20 50 40 100515 2 B 10 0 5 15 75515 2 C 10 20 40 10 20515 2 D 10 100 100 100 100515 2 I 25 20 30 75 100515 2 J 25 50 10 10 80515 2 K 25 20 80 100 100515 2 L 50 20 20 45 85515 2 M 50 5 30 30 85

The Golden Rule One Line = One Sample

Original data (1/6)

• Before all modifications, save a copy of the original table & make modifications to a copy that you can regularly save or back up.

Example: terrain2005ori.xls

terrain2005_05122006.xls

terrain2005_06122006.xls

etc.

Original data (2/6)

• In your Excel workbook, the sheet farthest to the left should contain ONLY the original data in a CONTINUOUS table

Date Point Parcelle Echelle haut midh midb bas502 1 A 10 50 40 20 70502 1 B 10 0 0 10 10502 1 C 10 0 0 10 10502 1 D 10 40 50 40 50502 1 I 25 0 70 100 100

Date Point Parcelle Echelle haut midh midb bas502 1 A 10 50 40 20 70502 1 B 10 0 0 10 10502 1 C 10 0 0 10 10502 1 D 10 40 50 40 50502 1 I 25 0 70 100 100502 1 J 25 0 0 25 70

Original data (3/6)

• NEVER leave cells empty

bloc couleur valeur

1 rouge 12

vert 18

bleu 44

2 rouge 15

vert 16

bleu 14

bloc couleur valeur

1 rouge 12

1 vert 18

1 bleu 44

2 rouge 15

2 vert 16

2 bleu 14

Original data (4/6)

• Missing data should be indicated by « . »

• Careful, always differentiate missing values from actual zero (0) values!!!

bloc couleur valeur

1 rouge 12

1 vert .

1 bleu 44

2 rouge 0

2 vert 16

2 bleu 14

Original data (5/6)

• Be consistent with your codes :

ABBA ≠ abba ≠ Abba

• Coding of numerical data with « . » or « , » will depend on what computer or operating system you use?If you aren’t sure…utilise the decimal key in the calculator section of the keyboard

bloc couleur valeur

1 Rouge 12

1 vert .

1 bleu 44

2 rouge 0

2 vert 16

2 bleu 14

Original data (6/6)

• Include cases where species have not been observed

(NB in ecology!!!)

Espèce Site Abondance

A 1 2

B 1 5

A 2 4

C 2 3

B 3 5

C 4 2

Espèce Site Abondance

A 1 2

B 1 5

C 1 0

A 2 4

B 2 0

C 2 3

A 3 0

B 3 5

C 3 0

A 4 0

B 4 0

C 4 2

Analysis of tables

Une feuille pour les données originales, les autres pour les

tableaux-croisés dynamiques ou les graphiques

• Move from left to right, ALWAYS keeping a sheet that contains the raw data.

Dynamic graphics and Cross tabulation

Data tables vs. Data bases

• A data table is organised by lines and by columns.

• A data base is a collection of data sheets & tables that allow you to store a great amount of information.

Conclusion

• Remain logical and structured.

• Include raw data.

• Save and back up, frequently.

• «Comments» sheet (measurement units, abbreviations, personnal notes …)

• REMEMBER:

The word «DATA» is plural!

The word «DATUM» is singular!

Questions?