CHAPTER 7 



Step-Functions 



7/1. Sometimes the behaviour of a variable (or parameter) can 

 be described without reference to the cause of the behaviour : if 

 we say a variable or system is a ' simple harmonic oscillator ' 

 the meaning of the phrase is well understood. Here we shall be 

 more interested in the extent to which a variable displays con- 

 stancy. Four types may be distinguished, and are illustrated in 



-^v 



D 



TIME— ►- 



Figure 7/1/1 : Types of behaviour of a variable : A, the full-function 

 B, the part-function ; C, the step-function ; D, the null-function. 



Fig. 7/1/1. (A) The full-function has no finite interval of con- 

 stancy ; many common physical variables are of this type : the 

 height of the barometer, for instance. (B) The part-function has 

 finite intervals of change and finite intervals of constancy; it 

 will be considered more fully in S. 14/12. (C) The step-function 

 has finite intervals of constancy separated by instantaneous jumps. 



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