Exercise 4: Wrking with tabular data Explring infant mrtality in the 1900s Backgrund Althugh peple tend t think abut GIS as being primarily cncerned with mapping. It is better thught f as a type f database that uniquely is able t explre spatial and attribute data tgether. This exercise will fcus n attribute data in tabular frm. It will examine a series f data surces frm the census and vital registratin data. In the first part f the exercise yu will explre basic selectin using attribute data. In the next part yu will explre the many tabular data management and viewing tls fr individual tables that are fund in ArcMap. In the final part f the exercise yu will learn t assciate tables in ArcMap by jining tabular datasets t spatial datasets. Data Surces These are again the same as the nes we started with, the layers frm the 1900s demgraphy map dcument. In this practical hwever manipulate these in a new map dcument. File Name RD1911 Reg_cunty Admin_cunty 1900s IMRs.xlsx Descriptin Shapefile cntaining Registratin Districts in 1911. Als has ppulatin density (pp_den) as an attribute. Shapefile cntaining the Registratin Cunties f England & Wales. Shapefile cntaining Administrative Cunties f England & Wales Excel attribute table frm the Registrar General s Decennial Supplement f 1911. These are listed by registratin district (reg_dist) and registratin cunty (GIS_Cnty) and gives the numbers f births (Births) and infant deaths (aged under 1) (I_death) thrugh the 1900s. 1911 Pp.dbf dbase attribute table frm the 1911 census. It is listed by registratin district (reg_dist) and registratin cunty (GIS_Cnty) and gives the year, ttal ppulatin (tt_pp) and ttal numbers f men and wmen (tt_male and tt_fem). GIS in the Digital Humanities 4-1
Summarized Guidelines fr Cmpleting Exercise The exercise will intrduce yu t: Basic querying f attribute data Hw t manipulate tables f attribute data t imprt data frm Excel, calculate new values, srt data, and find basic statistics abut it. Hw t jin tables with each ther. Summarising data. Step-by-Step Instructins First yu shuld use Windws Explrer t cpy the data fr the practical t the flder that yu want t wrk n it in. All the data shuld be in a the flder <My flder>\gis4. 1. Using queries Start ArcMap with a new Blank Dcument Add the Shapefile Rd1911 frm <My flder>\gis4 using the Add data buttn Right click n the Rd1911 icn n the table f cntents and select Open attribute table. Click n the Table Optins buttn in the tp left-hand crner f the Table windw and select Select by attributes (see belw). Duble click n Reg_Dist, single click n = and then click Get unique values GIS in the Digital Humanities 4-2
Scrll dwn the list f districts and duble click n Stepney The text bx shuld nw say REG_DIST = STEPNEY. Click the Apply buttn and then Clse. Click n the Shw selected recrds buttn at the bttm f the Table windw. The tw selected recrds are shwn in the attributes windw (as abve) In additin their plygns are highlighted with a blue utline n the Map windw. Under the cntext menu fr RD1911 chse Selectin > Zm t selected features. This will zm in n the district f GIS in the Digital Humanities 4-3
Stepney which is in central Lndn. Yu can see that Stepney district is in tw parts separated by a narrw crridr r, t put it anther way, there are tw plygns called Stepney which happen t belng t the same district. Chse the Select Features buttn n the Tls tlbar (circled abve) and click n the district that the narrw crridr belngs t. This selects it. What is the name f this plygn? What is its ppulatin density? Press the Clear selected features buttn, the ne belw f the Select Features buttn n the Tls tlbar shwn abve. Remve Rd1911 frm the map by right clicking n its name n the table f cntents and selecting Remve. This leaves yu with a blank map windw. GIS in the Digital Humanities 4-4
2. Explring and manipulating tabular data ArcMap can pen attribute data in a variety f frmats including Micrsft Excel, Micrsft Access, text, and Dbase (.dbf). Much f the functinality is nly available in Dbase files. Until recently Excel culd save spreadsheets as Dbase files but the newer versins f it d nt allw this. There are, hwever, ways f wrking rund this as we will see belw. In this sessin we will pen an Excel file cntaining infant mrtality rates (IMRs) and save it as a Dbase file fr further wrk. Start Micrsft Excel and pen the file 1900s IMRs.xlsx. Yu can see that this has fur clumns: Reg_dist: The name f the Registratin District Reg_Cnty: The name f the cunty that the registratin district is in Births: The number f births during the 1900s I_death: The number f infant deaths during the 1900s These are n a wrksheet called IMRs. There are tw ther wrksheets, Sheet2 and Sheet3 but these cntain n data. Once yu are happy with this clse Excel. GIS in the Digital Humanities 4-5
In ArcGIS press the Add data buttn and duble click n the 1900s IMRs.xlsx (d nt press the Add buttn at this stage). The three wrksheets will appear in the menu with $ signs after them. Add IMRs$, the wrksheet with data in it, either by duble clicking n it r by pressing Add. This will appear n the table f cntents. Right-click n the IMRs$ icn and select Open frm the cntext menu. The cntents f the spreadsheet shuld appear. Right click n the IMRs$ icn n the table f cntents and chse Prperties... and g t the Fields tab. This windw allws yu t explre the characteristics f the fields in the database, t change the rder that they appear in (using the arrws at the tp), and t hide fields. Click n GIS_Cnty and then uncheck the bx next t it (see belw, left) and click OK. Yu will see the item disappear frm the table (belw right). It has nt been deleted, it is merely n lnger being drawn. GIS in the Digital Humanities 4-6
Repeat this prcess but this time check the GIS_Cnty bx t re-draw the field. Right-click n the I_Death clumn heading and chse Srt Descending. This srts the list s the places with the largest numbers f deaths amng infants are at the tp. Srt Ascending gives the ppsite rder. Which district had the mst deaths? And which the fewest? Right-click n the I_Death clumn heading and chse Statistics. This prvides sme basic statistics abut the dataset including that there are 634 rws (cunt), a ttal f 1,186,621 infant deaths in England & Wales (sum), that the lwest number f deaths in a district was 30 (minimum) and the highest 26,679 (maximum). The average number f deaths was 1871.6 (mean). There is als a frequency distributin that shws that, like ppulatin density, the data were heavily skewed with a lt f districts having a small number f deaths and a few having a lt f deaths. Click n the red X in the tp-right f the windw t clse this. We need anther clumn that gives the infant mrtality rate, nt just the number f births and deaths. T d this we need t add a new clumn. ArcMap will nly allw us t explre Excel files, nt t change them. Instead we must first exprt it t a Dbase file and edit this. GIS in the Digital Humanities 4-7
Click n Table Optins menu and chse Exprt... and then use the brwse buttn t save a file called IMRs in yu GIS4 flder. Yu must change the Save as type: ptin t dbase Table. ArcMap autmatically adds the.dbf extensin. When yu are prmpted D yu want t add the new table t the current map? Click Yes. This adds a new table t the table f cntents called IMRs. Open this and yu will see that it lks very similar t the riginal table except there is a new clumn called OID. One imprtant difference is that if yu click n the Table Optins menu n the new IMRs table yu will see that Add Field is available. On the Excel versin it is nt. Nte als that when yu have tw r mre tables pen, they appear in the same widw, the tab at the bttm allws yu t swap between them GIS in the Digital Humanities 4-8
Remve the Excel versin (IMRs$) frm the table f cntents. Nw select the Add field ptin frm the Optins menu f the IMRs Dbase table. We want t add a field IM_rate f Type Flat (which means that it is a real number with decimal places rather than an integer). Click OK. A new field will be added and its values defaulted t 0. GIS in the Digital Humanities 4-9
Right-click n the heading f the IM_rate clumn and select the Field Calculatr. Click Yes if it gives yu a warning. An infant mrtality rate is calculated as the number f infant deaths per 1,000 births. T calculate this fill in the frm such that IM_rate = 1000* [I_death] / [Births]. Duble-clicking n the fields in the tp windw brings them dwn t the bttm windw. GIS in the Digital Humanities 4-10
Click OK. We nw have the new values as shwn belw. Nte that this new field has been permanently added t the Dbase table. GIS in the Digital Humanities 4-11
Using what yu have already learned find ut: Hw many districts have an infant mrtality rate f mre than 150? What is their average infant mrtality rate? Clse the Attribute table windw when yu have finished. GIS in the Digital Humanities 4-12
3. Jining Tables In the next part f the exercise yu will explre the tls that are used t jin tw r mre tables. This ability ffers a great deal f ptential t humanities research. Typically yu may have a set f plygns r pints representing administrative units r twns t which yu want t jin a range f tabular data frm ther surces. In the fllwing steps yu will jin the table cntaining the infant mrtality rates t the bundaries f 1911 Registratin Districts. Add the Rd1911.shp shapefile t the map using the Add data buttn Right-click the Rd1911 icn n the table f cntents and chse Open Attribute Table frm the layer cntext menu t pen the table. D the same with the IMRs table. Ntice that the REG_DIST field in the Rd1911 attribute table appears t have the same values as the REG_DIST field in the IMRs table. T verify that these values are the same, srt bth fields by chsing Srt Ascending ptin frm the Optins cntext menu fr each field. One thing t ntice is that smetimes a Reg_Dist n RD1911 can have mre than plygn s there are 736 rws f data n the Rd1911 attributes but nly 634 rws f data n IMRs. This was the case with Stepney as shwn earlier. GIS in the Digital Humanities 4-13
IMPORTANT! When yu jin tw tables in a real prject, remember the fllwing rules: The names f the fields that yu are ging t jin n (the key fields) in tw tables that yu wish t jin d nt have t be the same. The frmat f the key fields in tw tables that yu wish t assciate must be the same. In ther wrds, a text field will nt jin t a Lng Integer field. The lengths f the key fields in tw tables that yu wish t assciate d nt have t be the same. Yu d nt have t have the same number f recrds in tw tables t assciate them. Yu nly have t have at least sme matching values. Yu can have multiple key fields in a table. Hwever, nly ne key field can be used in any table jin. We will nw jin the IMRs table t the Rd1911 layer attribute table. Right-click the Rd1911 icn n the table f cntents and chse Jins and Relates > Jin frm the layer cntext menu. Cmplete the ptins in the Jin Data dialg bx as shwn in the fllwing example. This says that we will jin RD1911 t IMRs using the field Reg_Dist n bth tables. GIS in the Digital Humanities 4-14
Click the OK buttn t prcess this jin and t clse the Jin Data windw. Yu shuld nw see that the RD1911 table als has the attributes frm the IMRs table. GIS in the Digital Humanities 4-15
Nte that this has nt permanently changed either the shapefile r the Dbase table, the tables merely appear t have been jined. If yu save the Map Dcument the jin will be saved. If yu g t Prperties n the RD1911 cntext menu yu shuld be able t draw a map f 1900s infant mrtality rates as shwn belw. Yu can remve a jin by ging t RD1911 s cntext menu and ging t Jins and relates > Remve jins but d nt d this yet. GIS in the Digital Humanities 4-16
4. Summarizing data The IMRs table included a GIS_Cnty field which gives the name f the cunty that each registratin district lies in. In this sectin we will calculate the average infant mrtality rate fr each cunty and utput this t a new table. Open the attribute table f RD1911. Right-click n the clumn heading GIS_Cnty (a field frm the jined IMRs table)and select Summarise... GIS in the Digital Humanities 4-17
Use the + signs t pen the lists s that yu check the bxes fr Sum f Births (shwn belw), Sum f I_death, and Average f IM_Rate. Then click n the Flders buttn (circled). Put Cunty_IMRs as the Name, change Save as type: t Dbase Table and save it t the GIS4 flder. GIS in the Digital Humanities 4-18
Nw click Save and OK. When prmpted yu d want t add the new data t the map (click Yes). Nw pen the Cunty_IMRs table frm the Table f Cntents. Yu will see that it has five fields: GIS_Cnty: the name f the Cunty Cunt_GIS_Cnty: the number f rws f data that makes up this cunty Sum_Births: the ttal number f births in the cunty Sum_I_Death: the ttal number f deaths in the cunty Average_IM_rate: the average IM_rate fr districts in the cuntry. (Nte that this is nt exactly the same as the cunty s infant mrtality rate as in this field weights each district evenly. T be crrect, the cunty IMR shuld be calculated frm the sum_i_death and sum_births fields as this will give mre weight t districts with large numbers f births and deaths. Yu shuld als nte that even this may be wrng because where a district cnsists f tw r mre plygns it will be cunted mre than nce). 5. If yu have time. Remve RD1911 and IMRs frm the map. Add Reg_Cunty t the map Jin Reg_Cunty t Cunty_IMRs by jining frm the field Reg_Cunty t the field GIS_Cnty. Create a map f the average infant mrtality rates. Hw des this differ frm the registratin district level map. GIS in the Digital Humanities 4-19