5.9. Editing the symbol list¶
Clicking the button “Load symbols from equations” enables the symbol table for editing while the correct syntax of the equations is being checked with the internal function parser. In the case of an error corresponding warnings are given via Windows Message-box dialogs, which are acknowledged, and one has then look for reason behind that error message.
The symbol table consists of four text columns “Symbol”, “Type”, “Unit” and “Meaning”.
The symbols which were extracted automatically are characterised in the column “Type” as dependent (a) or independent (u) quantities, where the independent ones are listed first. Only the independent symbols (quantities) are the ones the measurement uncertainties of which are considered by the program. This is the important point which prevents at the very beginning that covariances could otherwise be inferred between dependent symbols because they would share common (independent) symbols.
Within the symbol list, such input quantities for which a mean and its uncertainty are to be derived from a data set, can be marked in the type column with “m“ instead of “a“ (dependent) or “u“ (independent). Furthermore, a quantity, to be derived by an equation, which shall be treated as a parameter without uncertainty, can be defined by sitting its type to “p“.
The columns “Unit” and “Meaning” are to be completed by the user. However, it is recommended to this later, at least after the equations have got their final state, because subsequent changes in the equations may lead to a different ordering of the symbols. This may also be postponed to a later session.
Due to subsequent changes within equations it may happen, that some of the symbols do not occur in the present set of equations. Such symbols are listed at the end of the symbol list, where they can be row-wise removed by the user (see below: Notes on editing tables).
After a mouse click inside a table mouse wheel scrolling is possible.
Very important:
Most often it is necessary to add manually such symbols at the end of the symbol table which do not explicitly occur in the equations but are needed within those formulae describing standard uncertainties; e.g. counting times tm or t0 are required to calculate the standard uncertainty of gross or background counting rates, sqrt(Rg / tm) or sqrt(R0 / t0), respectively.
