Combination of "for loop" and "if statement"

I have an assignment that requires me to use both 'for loop' and 'if statement'. However I have zero clue how to start. The question is something like:

machine runs at below 3 Knots means not working

machine runs at 3 to 5 Knots is average

machine runs at above 4 Knots is good

In my excel sheet I have one column for the time and another column matching it by side are the Knot values. I have a total of 400 plus data in my excel sheet.

How do i put this into codes when I was to find how long the machine spend running in total average speeed and how long running in good speed only?

Idk how to link the two coloumns tgt.

if ???
    if (y<3) 
        display ('not working') 
     elseif(3<y<5) 
        display ('average') 
     else(y>5)
         display('good') 
    end
end

[Steven Lord]

How would you do this if I gave you a list of times and speeds on paper, something like:

t = datetime('now', 'Format', 'HH:mm:ss');
times = t + minutes(cumsum(randi(10, 10, 1)));
speeds = round(2+4*rand(10, 1), 2);

results = table(times, speeds)

results = 10×2 table
     times      speeds
    ________    ______

    16:28:50     5.52 
    16:34:50     4.69 
    16:40:50     5.62 
    16:46:50     3.57 
    16:55:50     5.42 
    17:03:50     3.44 
    17:07:50     4.55 
    17:16:50     3.69 
    17:25:50     4.41 
    17:35:50     2.54 

Forget about doing this in MATLAB for right now. Break this down into the steps you'd follow. Do you start at the beginning, the middle, or the end? Do you work on each of the times first then each of the speeds or do you work on a row (time and speed) then proceed on to the next?

Once you know how to do this on paper, write those steps as comments in a MATLAB script file in the Editor. Then implement those steps in turn. If you're not sure how to accomplish a step, break it into substeps that you do and/or search the documentation for a term that's related to that step and see if there's a relevant function.

[Cynthia Lee]

Appreciate the help!

[Stephen23]

Original question by Cynthia Lee on 16th of March 2021, retrieved from Bing Cache:

http://web.archive.org/web/20210617175339/https://cc.bingj.com/cache.aspx?q=www.mathworks.com%2Fmatlabcentral%2Fanswers%2F771328&d=4993105852435017&mkt=en-WW&setlang=de-DE&w=B7AV5b6S2WDemhexTiAYu5AFnpS4pH62

http://web.archive.org/web/20210617175611/https://www.mathworks.com/matlabcentral/answers/771328-combination-of-for-loop-and-if-statement

I have an assignment that requires me to use both 'for loop' and 'if statement'. However I have zero clue how to start. The question is something like:

machine runs at below 3 Knots means not working

machine runs at 3 to 5 Knots is average

machine runs at above 4 Knots is good

In my excel sheet I have one column for the time and another column matching it by side are the Knot values. I have a total of 400 plus data in my excel sheet.

How do i put this into codes when I was to find how long the machine spend running in total average speeed and how long running in good speed only?

Idk how to link the two coloumns tgt.

if ???
    if (y<3) 
        display ('not working') 
     elseif(3<y<5) 
        display ('average') 
     else(y>5)
         display('good') 
    end
end

[Rena Berman]

(Answers Dev) Restored edit

Answer 1

[Walter Roberson]

rng(655321)
times = datetime('now') - minutes(sort(randi(600,10,1),'descend'))

times = 10×1 datetime array
   12-Mar-2021 15:26:03
   12-Mar-2021 16:13:03
   12-Mar-2021 17:05:03
   12-Mar-2021 17:07:03
   12-Mar-2021 18:53:03
   12-Mar-2021 21:06:03
   12-Mar-2021 21:49:03
   12-Mar-2021 21:57:03
   12-Mar-2021 23:06:03
   12-Mar-2021 23:28:03

knots = rand(10,1)*8

knots = 10×1

1.4359 6.3969 1.6781 3.2483 0.5765 4.2753 7.8071 1.1538 3.2355 2.5370

G = discretize(knots, [0 3 4 8], 'categorical', {'not working', 'average', 'good'})

G = 10×1 categorical array
     not working 
     good 
     not working 
     average 
     not working 
     good 
     good 
     not working 
     average 
     not working 

idx = find(G(1:end-1)=="good")

idx = 3×1

2 6 7

sum(times(idx+1)-times(idx))

ans = duration
   01:43:00

[Cynthia Lee]

sorry but I dont quite understand. Im still a beginner in MATLAB.

What happens when there are two seperate excel files that i need to use?

One file is the time and another file is the speed?

[Walter Roberson]

times = readmatrix('NameOfTimeFile.xlsx');
knots = readmatrix('NameOfKnotsFile.xlsx');

G = discretize(knots, [0 3 4 8], 'categorical', {'not working', 'average', 'good'});
idx = find(G(1:end-1)=="good");

good_times = sum(times(idx+1)-times(idx))

Note: this assumes that the "good" holds from the time it appears until the next time stamp that exists. There is an equally valid assumption that "good" should have been deemed to have held from the previous time until the time it appears. Neither one is "wrong", but they differ in how to treat a "good" that appears at the beginning or end of the data.

1 good
3 average
4 good

is that "good from 1 until 3, good from 4 but it is assumed it just got there; total good time 2" ? Or is it "good for some unmeasured time ending at 1, good from 3 ending at 4, total good time 1" ?

You can't have it both ways. Is the time the point at which the condition begins, or is the time when the condition ends?

[Cynthia Lee]

the speed excel matches the time excel. the speed have 450 values (ranging from 1-15) corresponding to the time excel of 450 minutes. each with a min difference. Sorry I wasnt clear.

I need to find out how many speed is from range 3-5 and above 5 and from there get their own individual time and add up the time it was average or good.

[Walter Roberson]

times = readmatrix('NameOfTimeFile.xlsx');
knots = readmatrix('NameOfKnotsFile.xlsx');

G = discretize(knots, [0 3 5 15], 'categorical', {'not working', 'average', 'good'});

average_times = nnz(G=="average");
good_times = nnz(G=="good");

[Cynthia Lee]

Appreciate your help!