If-Then-Else Statements

The syntax of the MATLAB If-Then-Else statement is as follows  

Note that the words if, else, and end are all lowercase. Statements and Statements2 can be any other MATLAB statements. The else clause is optional. 

---

As mentioned earlier, nonlinear objective functions are sometimes nonsmooth due to the presence of functions like abs, min, max, or if-then-else statements, which can cause derivatives, or the function itself, to be discontinuous at some points. Unconstrained optimization methods that do not use derivatives are often able to solve nonsmooth NLP problems, whereas methods that use derivatives can fail. Methods employing derivatives can get stuck at a point of discontinuity, but the function-value-only methods are less affected. For smooth functions, however, methods that use derivatives are both more accurate and faster, and their advantage grows as the number of decision variables increases. Hence, we now turn our attention to unconstrained optimization methods that use only first partial derivatives of the objective function. 

Turn off the flow by setting the value of TAU initially very high, and start the reactor as a batch system. Change over to continuous operation using the an IF-THEN-ELSE statement to define a value of TAU. 

The dimensionless model equations are programmed into the MADONNA simulation program HOMPOLY, where the variables, M, I, X and TEMP are zero. The values of the dimensionless constant terms in the program are realistic values chosen for this type of polymerisation reaction. The program starts off at steady state, but can then be subjected to fractional changes in the reactor inlet conditions, Mo, Io, T0 and F, of between 2 and 5 per cent, using the IF-THEN-ELSE statement and parametric run facility. The value of TIME in the program, of course, refers to dimensionless time. 

Study the MADONNA program so that the conditional logic based on the IF THEN ELSE statements is fully understood. 

The program employs an IF THEN ELSE statement to switch the feed rates. An alternative with the Windows version of MADONNA would be to use the CONTINUE feature. For this, the values of Nf would be changed after the STOPTIME was reached and the run continued with a new value of Nf and STOPTIME. 

The column start up is from an initial arbitrarily chosen composition profile. The steady state composition profile obtained from the first run can then be used as the starting profile for subsequent runs. With the MADONNA version for Windows, changes in operating parameters, such as feed rate, can be made with the CONTINUE feature. This can be programmed easily with IF-THEN-ELSE statements. In this way realistic dynamics can be obtained for the column conditions moving from one steady state to another. 

This can be done in two ways Either use the pre-programmed PULSE function (see the program CSTRPULSE for an example) or use an IF-THEN-ELSE statement to turn a stream on and off (see example CHROM). 

As the reader can see, a rule bears a close resemblance to an if-then-else statement, but unlike an if-then-else statement, it stands alone and does not fire in any predetermined order relative to other if-then-else statements. 

Note the change in the value of the proportional gain KP is changed at 90 h by use of an IF-THEN-ELSE statement ... 

Use switch construct instead of multiple, nested if-then-else statements, especially when all the conditionals are treated at the same level. The resulting code is usually easier to read and follow. However, when different types of conditionals are tested, multiple, nested if-then-else constructs are preferable. An example for using switch versus if statements is shown in Code Block 5 (Figure 2.5). 

The If... Then, Else statement has unrestricted length, and uses the syntax... 

When more than two choices must be considered in an If...Then, Else statement, these can be handled using If...Then, Elself, Else. In the above example one might instead write... 

The valves are straightforward and are often implemented as ideal diodes (for electrical circuit models) or as IF-THEN-ELSE statements (for algorithmic models) to keep all flows nonnegative. Defects in the valves can be added to simulate heart defects (e.g., leaky diodes for regurgitation). Other types of heart defects are just as easily simulated. For example, Blackstone et al. [1976] placed an impedance between the atrial chambers to simulate a septal opening. 

Figure 2 shows an example of a behavioral specification. It contains a simple VHDL program fragment, demonstrating assignment, arithmetic operations, a WHILE loop, and an IF...THEN...ELSE statement. 

After the SIFT vector sets have been converted to standard feature vectors, they are used to train a classifier. In this chapter, we report results of a bagged decision-tree classifier. A decision-tree classifier has the form of a nested set of if-then-else statements, where each statement has the form... 

Statement can either be a nested if then-else or else a predicted class label. A new specimen is assigned a predicted class by executing this tree of if-then-else statements until a predicted class label is reached. 

More complex policies can be defined by using if-then-else statements to select the appropriate proceed clause. Also, multi-level policies are possible with resolvers of resolvers. The AIRIA compiler checks that, whatever the join point, a unique root resolver manages conflicts at this join point. A total execution order must be obtained from the tree of resolvers starting from the root. 

If NdBNunbers > 0 Then begin an If-Then-Else statement... 

IF-THEN-ELSE. An if-then-else statement is one that causes the computer to decide whether an expression is true or false, but unlike the looping state-... 

The ELSE part of the statement is optional. If the else part is not used, the statement simply is called an if-then statement. Some examples of if-then-else statements... 

Closely related to the if-then-else statement is the LC IG if-xelse-end if statement. The long if is known as a branching statement. The syntax is... 

Like the if-then-else statement, the xelse is optional. A flow chart of the statements is shown in Fig. 11-1. An example of the use of a long if statement is... 

---