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--- en:lesson9 [2019/11/07 15:44]
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-FIXME **This page is not fully translated, yet. Please help completing the translation.**\\ //(remove this paragraph once the translation is finished)//
-====== Data Analysis ======
-===== Data Analysis with Excel =====
-Open the resulting data file with Excel. Press Ctrl-O and chose the folder containing the file. By default the Excel will not open txt form files, but when you enter * at the enter form and press Enter there will be displayed all files. Choose the data file and press Open.
-{{::09image001.png?nolink&400|}}
-This will start the import wizard. Press Next.
-On the first page specify the data form “with dividers”.
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-On the second page specify that column divider is the space character.
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-Make sure that in the window with example of the data presentation all columns are divided by vertical lines, than press Next.
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-Column’s data form must be leaved as “general”. Press “Finished”, the data will be written into Excel sheet.
-{{::09image006.png?nolink&200|}}
-Evidently, the data is divided by empty lines. To delete the empty lines select the first column.
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-Press F5, then press “Select” at the displayed window.
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-Check the box of “empty cells” and press ОК.
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-There will be selected all empty cells from the first column.
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-Now delete the lines where the empty cells are selected. Press.
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-Now the data are ready for analysis and diagrams’ plotting.
-{{::09image012.png?nolink&600|}}
-Please note! The first lines contain identical data because the OrbiCraft began rotation with delay of 5 seconds.
-Insert into document the point diagram with smooth curves and press the button for choosing data.
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-Press the button for adding data.
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-Do not enter the name of the row. Click “Х values” window and choose all cells from the first column by clicking at column’s header.
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-Then click “Y values”, delete “{1}” characters to leave equal mark only, and then choose the whole second column with data by clicking on the column header.
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-At the data source choose window there will be displayed the first data row.
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-Press ОК to close data choose window.
-Put the cursor to the top right corner of the second data column and drag it right to seize all data.
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-Select the columns from В to I.
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-Now the diagram will include all data collected from solar sensors.
-Please note the “outbreaks” at the diagram; it is measuring errors that are perfectly visible at the diagram.
-{{::09image029.png?nolink&400|}}
-Put the cursor at the “outbreak” and find the line with erroneous data in the table.
-{{::09image030.png?nolink&200|}}
-Please note that erroneous values are greatly different from adjacent values.
-{{::09image031.png?nolink&200|}}
-Manually change the incorrect values, changing them to the averages of the adjusting values.
-{{::09image032.png?nolink&200|}}
-The diagram plotted by the cleared data must be approximately like the one below:
-{{::09image033.png?nolink&400|}}
-Please note! The first lines contain identical data; it is evident from the diagram.
-===== Data preparation =====
-All decimal values in our table are pinned down to the left borders of the cells; it means that Excel interprets them as text data. For sure - the Excel uses for decimal numbers not a dot but comma character that divides the integer from its decimal part.
-We must replace all dots to commas in our file. To do so press Ctrl-H and enter in the upper window the dot mark, and in the lower window enter the comma mark.
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-Scroll down the table and memorize the last value of the measured angle.
-{{::09image035.png?nolink&600|}}
-Delete all data at the start of the table up to this angle.
-{{::09image037.png?nolink&600|}}
-Now the data will start and end from approximately the same angle; hence the OrbiCraft performed one revolution around its radial axis.
-Taking into account that magnetometer measures angles with some error, its readings is inadvisable base for positioning by solar sensors.
-Since OrbiCraft during data collection rotated equably we can calculate the precision angles.
-Count the overall number of the data lines (I personally counted 441 lines).
-{{::09image039.png?nolink&200|}}
-This number may be some less or some more depending on OrbiCraft rotation speed.
-Since the circle usually divided to 360 degrees, the angle value at every line of our table must differ from previous value for 360/441= 0,816327 degree.
-At the upper cell of the К column (К1 cell) copy the angle value from J1 cell.
-At К2 cell enter this formula:
-{{::09image040.png?nolink&100|}}
-Double-click lower-right corner of the К2 cell, the formula will be copied to all К column cells.
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-Now all angle values must be normalized to the range from -180 to 180 degrees.
-Find the line where angle value is more than 180 degree; change the formula in this line.
-{{::09image042.png?nolink&200|}}
-Formulas in the other cells must not be changed. Now all angle values in the table are in range from от -180 to 180.
-{{::09image043.png?nolink&100|}}
-For visual estimation of magnetometer error plot the diagram by outer right columns with angle values.
-{{::09image044.png?nolink&400|}}
-The diagram clearly shows that even the calibrated magnetometer is in error during angle measurement.
-Now we must delete all redundant data from the table.
-Copy К column and insert the data as values to L column.
-Now delete the J and K columns, also the first А column, with values of measurement time.
-Although in Excel the integer part divided from decimal by comma, the Python uses for this a dot. Using replace function (Ctrl-H) replaces all commas to dots in the file.
-{{::09image045.png?nolink&400|}}
-Now transfer all processed data back to Notepad++.
-Select all data in Excel and press Ctrl-C.
-Open Notepad++, create new project and insert the data using Ctrl-V.
-{{::09image046.png?nolink&400|}}
-Data inserted are divided by tabulation marks and line hyphen characters, but we need the division by  Python language rules – division by comma and space characters. Press Ctrl-H, enter \t to the upper window, enter comma with space character to the lower window. Press “Replace all” or “Replace in all open documents”.
-{{::09image047.png?nolink&400|}}
-Now we will replace the line hyphen characters in similar manner. Press Ctrl-H, enter \r\n to the upper window, enter comma with space character to the lower window. Press “Replace all” or “Replace in all open documents”.
-{{::09image048.png?nolink&400|}}
-Now all data are listed as one line. We will create the array based on this line. Save the data file in .txt form.

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