NUMERICAL COMPUTING For Finance Using Excel. Interpolation

Transcription

1 NUMERICAL COMPUTING For Finance Using Excel Interpolation

2 Outline 1 Excel Look-up Functions LOOKUP HLOOKUP VLOOKUP INDEX MATCH 2 Interpolation Linear interpolation (Cubic splines)

3 Excel Look-up Functions Fig(a) The Excel Lookup function is an in-built that returns a value from a range or array. For example, a lookup function may be implemented in Excel table of students detail such that it searches for a given student ID in a named column (e.g., column A) and return information (e.g. year of study) about the student in the same row (Row 5). Lookup function: =LOOKUP(value_to_lookup, data_to_search, results_column) NB: We are working with lookup vector. Fig (a) shows the table of student details we are working with.

4 Excel Look-up Functions Example: Use the Lookup function to find the Year of completion for student ID number Display completion year in cell C9. Type in cell C9 the following; =Lookup() and select lookup value, Lookup_vector, result_vector as in fig.(b). Fig. (b)

5 Excel Look-up Functions Use the Insert Function to display the function arguments dialogue box as in fig (c) below. Next, in the textbox for Lookup_value, insert the cell reference for the value In the textbox for Lookup_vector, select the range of cells (column) containing the looked-up_value (the column labelled Student ID). In other words, tell Excel what column to look for the value In the textbox for result_vector, select the range of cells containing the results you would like displayed. The column labelled Completion). In other words, tell Excel what to display when it finds the student ID. Fig.(c)

6 Code repositories What does the Error code #N/A in Excel imply? Why do we have #N/A in our diagram c) below?: 1 3 Fig. (d) The error in fig.(c) above is due the data range not sorted. Lookup function requires that the data be sorted in ascending order first

7 Excel Look-up Functions Your task: Sort the data in ascending order of the Lookup Value (Student ID) column. Fig (e) To sort the data, select the following range of cells: A2:F5. From the home tab and under the Editing group, click on the dropdown arrow next to sort & filter and select Sort smallest to Largest or A to Z. See results in fig (e).

8 Excel Look-up Functions Now, select the appropriate cell for the lookup value as in fig(c) and click Ok (see fig(f) and fig(g). Fig(f) Fig(g)

9 HLOOKUP and VLOOKUP Functions VLOOKUP The VLOOKUP function is used to find things in a table or range of searching for the lookup value and returning the corresponding data or variable or attribute. =VLOOKUP(lookup value,table array,column index number,range lookup) Lookup value is the value to be found. Table array range of cells or table to be searched for the lookup value and the data to be returned. Column index this is the column containing the data to be returned. Range lookup 0 or false for exact match, 1 or true for approximate or the next best thing. Range lookup value is optional, but very important

10 HLOOKUP and VLOOKUP Functions VLOOKUP Question: a) Use exact VLookup b) Use inexact VLookup to find the grade for a student who scored: i) 60% ii) 65% iii) 100% Fig (i)table of scores and Grade

11 HLOOKUP and VLOOKUP Functions VLOOKUP In cell D14, type in the VLOOKUP formula and use the insert function to display the function argument dialogue window below. In the Lookup_value textbox, select cell C14. In cell C14, we will later type in the score of the student. We are currently working with a range (not a table). In the Table_array textbox, select the range of data A3:B7. The value we want to display (Grade) is in column 2 of our range of data so type in 2in the textbox where it says Col_index_num Fig (ii) Finally in Range_lookup, type in 0 or FALSE for exact VLookup.

12 HLOOKUP and VLOOKUP Functions VLOOKUP fig (iii) fig (iv) Repeat the process for 65% and 100%

13 HLOOKUP and VLOOKUP Functions VLOOKUP Why is it giving us the error code #N/A? How do we fix this #N/A error?

14 HLOOKUP and VLOOKUP Functions VLOOKUP For INEXACT VLOOKUP, We type 1 or TRUE in the textbox for Range_lookup: Typing in 1 or true allows Excel to give us the next best thing (or closest match). This way, there is always going to be a returned value. Apart from a few circumstance, this is usually not advisable.

15 HLOOKUP and VLOOKUP Functions HLOOKUP This is very much similar to the VLOOKUP except that it is used when the data being searched is horizontally orientated. Search for a lookup value in the first row of a two-dimensional array: =HLOOKUP(lookup value,table array,row index number,range lookup) Lookup value value to be found Table array range of cells to be searched and data to be returned Row index row containing value to be returned Range lookup 0 or false for exact match, 1 or true for approximate