The document presents a simple C program demonstrating a moving average filter for time-series data aimed at aspiring C or C++ developers. It includes details on data types, control flow, and sample input/output for calculating averages from user input. Additionally, it discusses coding considerations, optimization techniques, and applications related to signal processing filters.

1. Moving Average in C
C Program for a Moving Average Filter
Colin McAllister, 24/7/2017

2. Moving Average in C
 A simple C program to transform input data to
output data. (Time-series data)
 Purpose: Demonstration of C programming.
 Audience: Aspiring C or C++ Developers.
 Model: A simple signal processing example.
 Features: data types, control flow, floating point
numbers, program input and output.

3. Block Diagram of Filter

4. Data Types
 0,1 – Boolean constants (False,True)
 int – Signed integer
 unsigned int – Unsigned integer
 double – Floating point (real) number
 double x[t], y[t] – Arrays of data

5. C Language Features
 main() function
 Program input - scanf()
 Program output - printf()
 Control flow – A simple “while(True)“ loop
 Blocks of code – Bound by “{“ and “}“
 Data types – assignment (equals sign “=“)
 Floating point numbers – Average value

6. Integrated Development Environment

7. Hello World Template

8. First Draft of Program

9. Input and Output of Floating Point
Program Statements
puts("Moving Average"); /* output */
puts("Enter sample"); /* output */
scanf("%lf", &value_in); /* input */
printf("Input value %fn", value_in);
Terminal Window:
$ ./MovingAvg
Moving Average
Enter sample
12.34
Input value 12.340000

10. Calculate Average of Three Numbers
#define SAMPLES 3
double x[SAMPLES];
double value_in, avg;
int i;
int main(void) {
puts("Moving Average"); /* output */
printf("Enter %d samples:n", SAMPLES); /* output */
for(i=0; i<SAMPLES; i++)
{ scanf("%lf", &value_in); /* input */
x[2]=x[1];
x[1]=x[0];
x[0]=value_in;
avg = (x[0]+x[1]+x[2])/3.0;
printf("Average %fn", avg);
}

11. Calculate Average – Terminal Window
 $ ./MovingAvg
 Moving Average
 Enter 3 samples:
 1.0
 Average 0.333333
 2.0
 Average 1.000000
 4.0
 Average 2.333333

12. Shift Data and Calculate Average

13. Shift Data and Calculate Average (Detail)

14. Shift and Calculate – Terminal Window
 $ ./MovingAvg
 Moving Average, Window Size 3
 Enter many samples:
 2.0
 x 0.000000, y 0.666667
 2.0
 x 2.000000, y 1.333333
 2.0
 x 2.000000, y 2.000000
 0.0
 x 2.000000, y 1.333333
 0.0
 x 0.000000, y 0.666667
 0.0
 x 0.000000, y 0.000000

15. Your Questions or Comments?
Clip art from www.123rf.com

16. Coding Considerations
 Develop in your favourite IDE
 Fix compiler errors and warnings
 Use Debugger to step through code
 Make code modular – Use functions
 Port program from C to C++
 Use OOP features of C++
 Use modern containers and iterators
 Try different compilers or even languages

17. Application Considerations
 Applications: Read about FIR Filters
 Optimisation: Avoid shifting the data
 Optimisation: Replace double with int
 Generate test data using Trig functions
 Generate noisy test data using rand()
 Use filter to improve Signal/Noise ratio
 Frequency response of Low pass filter
 Plot graphs to visualise Filter operation