gibson:teaching:spring-2016:math445:lecture:forloop
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gibson:teaching:spring-2016:math445:lecture:forloop [2016/02/16 11:47] gibson |
gibson:teaching:spring-2016:math445:lecture:forloop [2016/02/17 07:38] (current) gibson |
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| * ''%d'' decimal (integer), e.g. 5 | * ''%d'' decimal (integer), e.g. 5 | ||
| * ''%f'' floating-point, e.g. 2.75 | * ''%f'' floating-point, e.g. 2.75 | ||
| + | * ''%e'' floating-point in scientific (exponential) notation, e.g. 2.75e+00 for 2.75 | ||
| * ''%s'' string (a sequence of characters), e.g. '' 'banana'''. | * ''%s'' string (a sequence of characters), e.g. '' 'banana'''. | ||
| * ''%c'' character, e.g. '' 'q' '' | * ''%c'' character, e.g. '' 'q' '' | ||
| + | |||
| + | The decimal and floating-point slots can be specialized to print numbers in particular ways, for example, | ||
| + | |||
| + | <code matlab> | ||
| + | >> fprintf('The value of pi is %8.3f\n', pi) | ||
| + | The value of pi is 3.142 | ||
| + | </code> | ||
| + | |||
| + | This prints $\pi$ with 3 digits after the decimal in a fixed-width field of 8 characters. | ||
| + | |||
| + | You can put as many slots in a format string as you like. Just provide as many variables as slots, and make sure the types of the slots match the variables. | ||
| + | |||
| ===== for loops: repeating sequences of commands===== | ===== for loops: repeating sequences of commands===== | ||
| Line 76: | Line 89: | ||
| ===== example functions ===== | ===== example functions ===== | ||
| - | ====mysum==== | + | ==== sum the components of a vector ==== |
| This ''mysum'' function computes the sum of the components in the input vector $x$. There are a | This ''mysum'' function computes the sum of the components in the input vector $x$. There are a | ||
| number of extraneous print statements which show how the calculation works, step-by-step. | number of extraneous print statements which show how the calculation works, step-by-step. | ||
| Line 138: | Line 151: | ||
| end | end | ||
| </file> | </file> | ||
| - | ===== example function: myfactorial ===== | + | ==== compute the factorial ==== |
| + | |||
| + | This function computes $n!$, the factorial of $n$, according to the formula | ||
| + | |||
| + | \begin{eqnarray*} | ||
| + | n! = \prod_{i=1}^n i = 1\cdot 2 \cdot 3 \cdot \ldots \cdot (n-2) \cdot (n-1) \cdot n | ||
| + | \end{eqnarray*} | ||
| <file matlab myfactorial.m> | <file matlab myfactorial.m> | ||
| Line 145: | Line 164: | ||
| p = 1; % variable to store partial products | p = 1; % variable to store partial products | ||
| - | |||
| - | fprintf('Will need to do %d products.\n', n); | ||
| | | ||
| % each step through the loop does one more multiplication | % each step through the loop does one more multiplication | ||
| % in the sequence of products 1, 1*2, 1*2*3, etc. | % in the sequence of products 1, 1*2, 1*2*3, etc. | ||
| for i=1:n | for i=1:n | ||
| - | fprintf('The current value of p is %f.\n', p); | ||
| - | pause | ||
| - | fprintf('Multiply p by %f.\n', i); | ||
| p = p * i; | p = p * i; | ||
| end | end | ||
| - | + | ||
| - | fprintf('The current value of p is %f.\n', p); | + | |
| - | pause | + | |
| end | end | ||
| </file> | </file> | ||
gibson/teaching/spring-2016/math445/lecture/forloop.1455652048.txt.gz · Last modified: 2016/02/16 11:47 by gibson
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