### Frequently Asked Questions about Igor

#### Why can long, descriptive wave names cause problems?

Although Igor allows you the freedom to name your wave why I love to make my wave names so descriptive, you’ll save yourself headaches by avoiding spaces in wave names. Waves are identified by their names. The first space appears to end the wave name, unless you surround the whole name with single quotes: 'why I love to make my wave names so descriptive'.

#### Why shouldn’t I put units in wave names?

Igor has a nifty way of associating physical dimensions to both the values in a wave and to its scaling. If you use the Sample Variance panel from the HMC menu, you have a direct means of entering units. Alternatively, use the Data|Change Wave Scaling… command.

#### Why shouldn’t I change the name of a column?

Coming from a spreadsheet, a natural way to change the name of a data column would be to edit the column head. Unfortunately, in Igor this does not do what you think it might. It doesn’t change the name of the wave shown in the column, it merely changes its label in the table. So, don’t double-click to edit the column head; right-click to Rename the wave.

Look carefully at the title bar of the window shown above, which lists the names of the three waves shown in the table. The middle wave is listed as wave0 in the title bar, but as height in the body of the table. Why? Because the text of the column head was changed, not the wave name itself, probably by double-clicking on the column head and filling out the Title box near the bottom of the dialog shown here.

Moral: do not double-click on the column head to change the title; right-click on the column head and choose Rename... from the popup menu.

#### Why won’t my error wave show up in the fitting dialog?

There a few different possibilities that could cause this problem. The first thing to check is whether your data is in a text wave, not a numeric wave. This can happen because you imported from a file and the titles at the top of the file confused Igor or because the first thing you typed in a new column of a data sheet was text, not numbers. Igor has to decide whether to create a text or numeric wave when you begin a new column. It takes its cue from the first thing you type. So, be sure to type a number first. To check whether your wave is a text wave, locate it in the Data Browser (in the Data menu). Then check the information supplied when you click on the wave's icon, as illustrated in the figure.

If the wave is a text wave, you can convert it to a numeric wave with the command toNumeric(wavename), if you have installed the HMC menu.

Another possibility is that the wave you want to reference doesn't have the same number of points as another wave you are using. For example, if you are running a fit and trying to use a wave for uncertainties, unless the wave with uncertainties has the same number of points as the $$y$$ wave, it won't show up as a possible wave in the fitting dialog. The figure illustrates the problem, which you can fix by right-clicking on the extra cell(s) and deleting the corresponding points from the wave.