OpenOffice.org OpenOffice - 3.3 Guía básica descargar pdf (Pagina 160)

Introduction

In previous chapters, we have been entering one of two basic types of data into each

cell: numbers and text. However, we will not always know what the contents should

be. Often the contents of one cell depends on the contents of other cells. To handle

this situation, we use a third type of data: the formula. Formulas are equations using

numbers and variables to get a result. In a spreadsheet, the variables are cell

locations that hold the data needed for the equation to be completed.

A function is a predefined calculation entered in a cell to help you analyze or

manipulate data in a spreadsheet. All you have to do is add the arguments, and the

calculation is automatically made for you. Functions help you create the formulas

needed to get the results that you are looking for.

Setting up a spreadsheet

If you are setting up more than a simple one-worksheet system in Calc, it is worth

planning ahead a little. Avoid the following traps:

• Typing fixed values into formulas

• Not including notes and comments describing what the system does, including

what input is required and where the formulas come from (if not created from

scratch)

• Not incorporating a system of checking to verify that the formulas do what is

intended

The trap of fixed values

Many users set up long and complex formulas with fixed values typed directly into

the formula.

For example, conversion from one currency to another requires knowledge of the

current conversion rate. If you input a formula in cell C1 of =0.75*B1 (for example to

calculate the value in Euros of the USD dollar amount in cell B1), you will have to

edit the formula when the exchange rate changes from 0.75 to some other value. It is

much easier to set up an input cell with the exchange rate and reference that cell in

any formula needing the exchange rate. What-if type calculations also are simplified:

what if the exchange rate varies from 0.75 to 0.70 or 0.80? No formula editing is

needed and it is clear what rate is used in the calculations. Breaking complex

formulas down into more manageable parts, described below, also helps to minimise

errors and aid troubleshooting.

Lack of documentation

Lack of documentation is a very common failing. Many users prepare a simple

worksheet which then develops into something much more complicated over time.

Without documentation, the original purpose and methodology is often unclear and

difficult to decipher. In this case it is usually easier to start again from the beginning,

wasting the work done previously. If you insert comments in cells, and use labels and

headings, a spreadsheet can be later modified by you or others and much time and

effort will be saved.

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OpenOffice.org OpenOffice - 3.3 Guía básica Pagina 160