Perfil BIOII (Montemorelos, N.L., altitud: 1166 msnm)

The plain view selection presents the data set as it is stored in the spreadsheets. Tufte (1983, p.27) suggests that the time-series plot is the most frequently used form of graphic design. In a random sample of 4000 graphics drawn from 15 of the world's new papers and magazines published from 1974- 1980, Tufte found more than 75% were time-series. A time-series view of the data is provided for this important kind of data set to enable the user to carry out tasks such as trend analysis and data comparison.

An integrated view is particularly useful for multi-dimensional data as it allows the user to take a global view of the data to support decision making tasks. Various representations of the multi-dimensional data, such as Chemoff faces, stars and glyphs, are available for different types of decision making tasks. Figure 6.8b shows how the user can select various facial attributes to represent the multi-dimensional data.

P l a i n Uiew

Tim e S e ries Uiew

I n teg rated ll i e w � C:hernoff Fa£:es ... G l y phs .. . Sta rs .. . Tre es a n d C a s t l e s ... (a) I n t e g ra t ed Uiew - Chern o ff F a c e s D a t a S c i e n c e Re pre s en t a t ion L e ngth of Nose C urua t u re o f Mouth O K (b)

Figure 6.8 The menu and dialogue box for specifying an integrated view. (a) The menu for selecting an integrated view of data. (b) The user can select various facial attributes to represent the data.

CHAPTER 6: DESIGNING THE INFOLENS

Filter _{Filter Control}

124

This control allows data within a selected range as specified by the user to be identified quickly. This feature of the lnfoLens is particularly useful in situations where the user may wish to examine data which satisfy certain criteria. When this icon is activated, the system prompts a dialogue box to enable the user to select the attributes and their ranges.

F i l t er Contro l

D a t a Selected R a n g e

1 English From: 50 To:

2 M a t h s From: 50 To:

3 Fre nch From: 50 To:

4 S c i e n c e From: To:

H n d O r (

)

F i l t e r EHpre ss i on: 1 and ( n o t

2)

OK

Figure 6.9 A dialogue box for specifying the Lens Filter

Figure 6.9 shows the arrangement of this dialogue box. In this example, the user selects the students' subject scores in English, Maths and French which have a value of ₅₀ or higher. The user can then use the mouse and the selection buttons to create a logical fllter expression; in this case, the user is interested in examining the marks where a student passes both English and French but fails Maths.

CHAP1ER 6: DESIGNING THE INFOLENS

Navigation controls

125

In the context of the lens metaphor, the navigation controls are analogous to the panning action of the lens over the information space. The scroll bars in the display area support this operation and the navigation controls provide a finer manipulation of the panning action in a number of ways. First, whilst the scroll bar supports four directions of movement, the navigation control provides eight possible directions of movement. Second, the panning action may be activated continuously by depressing the mouse button when the cursor is placed on one of the eight arrows in the navigation controls. The use of morphing algorithm would allow the user to pan across the information space fluidly as if he or she was holding a magnifying lens. This feature is desirable as empirical findings in Chapter 3 suggest that a user performs better with a scrolling interface than with a point and click interface. Third, the gain control of the scroll movement may be adjusted. This is achieved by progressively activating the '-' or '+' button in navigation controls using a mouse, with a corresponding decrease or increase in the gain control of the scroll movement When one extreme of the setting is reached, the inactive button is dimmed, thus allowing the setting to be changed in the opposite direction. The bottom scroll bar mechanism allows the user to adjust the scrolling speed quickly.

In addition to the above navigation controls, the user may also move the central focus area from one point of the information space to another quickly using a point and click action, directly manipulating on the display area.

D

As the tasks of interpreting an item and relating it to other items within various locations in the information space are frequently executed, special facilities to support these tasks would be of great practical value to the user. The container is a temporary storage area which enables a set of selected items to be compared later. The user may put an item of interest into the container by dragging it from the display area; an array of data may also be deposited in a similar way by marking them in the display area first. To provide immediate and useful visual feedback to the user, a marker is generated automatically in the container in the position relative to the entire information space. The size of the markers is proportional to the number of items selected. An item may be

CHAPTER 6: DESIGNING THE INFOLENS 126