OpenOffice.org OpenOffice - 3.3 Podstawowy Przewodnik Pobierz pdf (Strona 182)

Break formulas into parts and combine the parts

The second strategy is similar to the first, but instead you break down longer

formulas into smaller parts and then combine the parts into the whole. Many

examples of this type exist in complex scientific and engineering calculations where

interim results are used in a number of places in the worksheet. The result of

calculating the flow velocity of water in a pipe may be used in estimating losses due

to friction, whether the pipe is flowing full or partially empty, and in optimizing the

diameter for the given flow regime.

In all cases you should adopt the basic principles of formula creation described

previously.

Use the Basic editor to create functions

A third strategy is to use the Basic editor and create your own functions and macros. This

approach would be used where the result would greatly simplify the use of the spreadsheet

by the end user and keep the formulas simple with a better chance of avoiding errors. This

approach also can make the maintenance easier by having corrections or updates kept in

one central location. The use of macros is described in Chapter 12 of this book and is a

specialized topic in itself. The danger of overusing macros and custom functions is that the

principles upon which the spreadsheet is based become much more difficult to see by a

user other than the original author (and sometimes even by the author!).

Finding and fixing errors

It is common to find situations where errors are displayed. Even with all the tools

available in Calc to help you to enter formulas, making mistakes is easy. Many people

find inputting numbers difficult and many may make a mistake about the kind of

entry that a function's argument needs. In addition to correcting errors, you may

want to find the cells used in a formula to change their values or to check the answer.

Calc provides three tools for investigating formulas and the cells that they reference:

error messages, color coding, and the Detective.

Error messages

The most basic tool is error messages. Error messages display in a formula’s cell or

in the Function Wizard instead of the result.

An error message for a formula is usually a three-digit number from 501 to 527, or

sometimes an unhelpful piece of text such as NAME?, REF, or VALUE. The error

number appears in the cell, and a brief explanation of the error on the right side of

the status bar.

Most error messages indicate a problem with how the formula was input, although

several indicate that you have run up against a limitation of either Calc or its current

settings.

Error messages are not user-friendly, and may intimidate new users. However, they

are valuable clues to correcting mistakes. You can find detailed explanations of them

in the help, by searching for Error codes in OpenOffice.org Calc. A few of the most

common are shown in the following table.

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