Dear all, how can I solve the index exceed the number of array problem?

Index exceeds the number of array elements (0).

water_level_time1 = Waterlevel_P1(:,1);

water_density = 1000;

weather_pressure = [];

for i=1:size(Waterlevel_P1,1)

index = find(water_level_time1(i) == weather_time);

if size(index, 1) > 0

weather_pressure(i, 1) = Pressure(index(1));

else

previous_elements = find(weather_time < water_level_time1(i));

next_element = find(weather_time > water_level_time1(i));

weather_pressure(i, 1) = (Pressure(previous_elements(end)) + Pressure(next_element(1)))/2;

end

end

[Sindar]

use code blocks (see toolstrip) and copy the full error text when asking questions

[Caroline Ganglo]

Thanks for your comment,

here is the loop created, and the error.

water_level_time1 = Waterlevel_P1(:,1);

water_density = 1000;

weather_pressure = [];

for i=1:size(Waterlevel_P1,1)

index = find(water_level_time1(i) == weather_Time);

if size(index, 1) > 0

weather_pressure(i, 1) = Pressure(index(1));

else

previous_elements = find(weather_Time < water_level_time1(i));

next_element = find(weather_Time > water_level_time1(i));

weather_pressure(i, 1) = (Pressure(previous_elements(end)) + Pressure(next_element(1)))/2;

end

end

Here is the error

Index exceeds the number of array elements (0).

Error in Water_level_combined_data_151020 (line 62)

weather_pressure(i, 1) = (Pressure(previous_elements(end)) + Pressure(next_element(1)))/2;

Answer 1

[Walter Roberson]

When the water level time is larger than anything in the array then the next element list would be empty and index 1 of it would be out of range.

By the way, have you considered using interp1 with extrapolation turned on?

[Caroline Ganglo]

Dear Walter,

thanks for your comment, I am fairly new to matlab and

the idea is to find equivqlent between the water level time and the weather time. Does the size matter?

I have not used the above mentioned function. Please how do they apply?

[Walter Roberson]

Your code is asking whether there is an exact match and if not taking the mean of the two adjacent entries. But suppose that you are asking about something that is before the first or after the last one?

Are you sure mean of the adjacent entries is best? Suppose you miss by 1 minute and the next on the other side is an hour away, then should the contribution from one minute away be equal to the contribution from an hour away, or should the contributions be weighted by how close they are?

[Caroline Ganglo]

The water level time is at 15 mins interval while the weather time is at 1 min. In this case can I still use the code or what is the best option?

[Walter Roberson]

Best option for that kind of situation is probably converting the data into a timetable() and using retime()