I want compare the differences from each block of 10 values to the next block of 10 values until the given 100 sets of values are compared.

I want to compare first 10 data with the next 10 data using a while loop. I have coded for first 10 values and have obtained the plot. In the same way I need to obtain it for next 10 sets of values until 100 sets of values are completed. For this I need to code using i,j values something in this format x = a(j:j+1). Please help me with this code

clc;
close all;

x = a(1:11)
while n < 12
    y(n) = a(n) - a(n-1);
    n = n + 1
end
plot(y)

[Dyuman Joshi]

"I want to compare first 10 data with the next 10 data using a while loop. I have coded for first 10 values and have obtained the plot."

In your code, you have compared N th value to N+1 th value.

Do you want to compare a(1:10) to a(11:20), a(11:20) to a(21:30) and so on?

Or do you want to compare numbers in pairs for group of 10 numbers? (1-2, 2-3, 3-4,...)

[Surabhi A S]

I just want to compare first 10 values to next 10 like a(1:10) to a(11:20) and so on.I want to know if the graph is increasing or decreasing, like if the difference is positive then its increasing in the graph else decreasing and if both are same then constant. I just want to compare them in plot(graph) for 1000 values.

[Image Analyst]

@Surabhi A S did you try, or even see, @Jan's answer below? Scroll down.

[Surabhi A S]

Yes I saw it. But I haven't tried it yet. I'll try it once

Answer 1

[Jan]

According to the text of the question (but not the posted code):

A = rand(100, 1);
B = reshape(A, 10, 10);
C = diff(B, 1, 1);
plot(C)

while-loops are useful if the limits are determined dynamically. Use a for-loop for known limits or a “vectorised” approach using arrays as above.

[Surabhi A S]

Thank you for the answer. But I have a doubt, does rand take values randomly between 1 to 100? Or in an ascending order?

[Image Analyst]

@Surabhi A S, no -- rand takes the number of rows and number of columns you want. It returns the random numbers. If you want to create a random vector for sample data that is 1000 long and in the range 0-100, and sorted, you'd do

A = sort(100 * rand(1000, 1), 'ascend');
B = reshape(A, 10, []);
size(B)

ans = 1×2

10 100

C = diff(B, 1, 1);
size(C)

ans = 1×2

9 100

plot(C)

[Surabhi A S]

Ok, thank you. Let me just tell you clearly what I actually need.

I have an excel or matrix of 1000 points( it has 1 row and 1000 columns). If I plot this in MATLAB I obtain a graph which has several ups and downs. So i want to compare at which point or the column its going up and which point its coming down. For this I want to compare a block of 10 points to the next block of 10 points and see if its increasing or decreasing. This cam be done using while loop as shown in the code i guess. If there is any other easy way to compute for 1000 points directly let me know.

Thanks in advance

[Jan]

You have a [1 x 1000] vector.

"So i want to compare at which point or the column its going up and which point its coming down."

This would be done by: diff(x) >= 0 . Not loop required.

"I want to compare a block of 10 points to the next block of 10 points" - this is still unclear. What does "compare 10 points" mean? The average of points 1:10 compared with 11:20? Or 1:10 with 2:11? The difference between such blocks, or the RMS?

While using while or for loops is a simple question and a vectorized is easy also, the problem is not explained mathematically yet.

[Surabhi A S]

I require a loop as I am collecting real time data as well. If not I would use diff function. I want to compare 10 points mean: a(1:2) with a(2:3) with a(3:4) and so on till 1000 points are completed. If a(3:4) > a(2:3) > a(1:2) then the graph is increasing.

[Jan]

@Surabhi A S: Sorry, I still cannot follow your explanations. Why is "a(1:2) with a(2:3) with a(3:4) and so on" a "10 points mean"? It does neither concern 10 points nor a mean.

If you have this input:

a = reshape(magic(5), 1, [])

a = 1×25

17 23 4 10 11 24 5 6 12 18 1 7 13 19 25 8 14 20 21 2 15 16 22 3 9

what is the wanted output?

[Surabhi A S]

If I have this input I require an output as the index at which 4 occurs

[Jan]

What does this mean? Do you mean, that the wanted output is the scalar 3?

"If a(3:4) > a(2:3) > a(1:2)" - This is not meaningful in a mathematical sense. Remember that the if command needs a scalar condition, but a(3:4) > a(2:3) is a vector.

After discussing for 3 weeks now, I still do not have any idea about what you want to achieve. I give up here. Good luck!

[Surabhi A S]

@Jan Thank you for your efforts. Let's make a last try if you can understand it by this flowchart what I exactly want else no problem.

[Jan]

@Surabhi A S: You ignore my questions for clarificationsm but introduce new information ("Z positive for more than 5 points"), which do not match the formerly given details. The instruction "fall is detected" is not clear.

Of course I could try to guess, what you want, but this is neither efficient nor trustworthy.

Before you can write a program, you need a clear and clean idea of what you want to achieve.